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Authorship：Lead author   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/min9120791

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Lithium cobalt phosphate, LiCoPO4, has attracted much attention as a high voltage cathode material in lithium ion batteries (LIBs). Since this material suffers from very low ion and electron conductivities, the composite structure made with nano-sized LiCoPO4 and carbon can be effectively used as a cathode material. Here, we report a simple mechanical synthesis route for preparing LiCoPO4/C composite granules. The raw materials for LiCoPO4 and carbon were mechanically treated with an attrition-type mill for producing LiCoPO4/C composite granules using a one-step process without employing external heating. With an increase in the amount of carbon used, the primary particle size of LiCoPO4 and the median size of granules were decreased. The first discharge capacity obtained for the LiCoPO4/C prepared with 5 mass% carbon was 105 mA h g(-1), whereas a value of up to 134 mA h g(-1) was obtained for the composite with 10 mass% carbon. We examined the effect of carbon addition on the mechanical synthesis and characteristics of LiCoPO4 powders.

DOI： 10.1016/j.ceramint.2016.10.022

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：SOC CHEMICAL ENG JAPAN  

Some of the many kinds of sulfide ore previously produced in Japan have generated acid mine drainage (AMD) by exposure to oxygen in groundwater or air after closure of the mines. AMD is typically treated by neutralization with lime (Ca(OH)(2)) or calcium carbonate (CaCO3). This process can remove many toxic elements from the AMD in a simple way, but the amount of neutralizer used is often decided based on experience because the removal mechanism of each element has not been quantified. Seasonal variation in the quality and quantity of AMD is considerable, and for many mines their AMD needs to be treated semi-permanently. Thus, more efficient and stable treatment is required in order to reduce chemical input and sludge generation.
With a view to construction of a more efficient AMD treatment method and process, this study aims to develop a simulator that can represent water quality. To this end, a quantitative model that can represent changes in pH and the concentration of each element was constructed using a chemical equilibrium calculation that incorporates surface complexation by ferrihydrite and aluminum hydroxide, which have the potential to remove many kinds of toxic elements. For the surface complexation model of each hydroxide, the double layer model was used. By comparing the calculated results with experimental results obtained from neutralization of two kinds of actual AMD, it was confirmed that the quantitative model constructed in this study could successfully represent the changes in pH and residual concentration of each element.

DOI： 10.1252/kakoronbunshu.43.207

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：SOC CHEMICAL ENG JAPAN  

The recent dramatic increase in demand lithium ion batteries (LIBs) in the automotive and electronic industries makes it desirable to establish sustainable recycling technology to recover cobalt from the cathode material (LiCoO2). Although the combination of physical and hydrometallurgical processes is one option for recovery of metals, the large amount of aluminum in the cathode of spent LIBs can negatively affect the process performances. Therefore, as a means to enhance the cobalt recovery from spent LIBs, we investigated the feasibility of a physical process for separation of cobalt and aluminum by thermal treatment and wet magnetic separation. Results highlighted the efficiency of the thermal treatment for conversion of the cathode material to magnetic cobalt due to (i) the presence of the more reactive lithium-deficient LixCoO(2) (x< 1), (ii) the presence of reductive aluminum and graphite from electrode supports, and (iii) the generation of CO, CH4 and C2H4, which activate reduction and carbonation. Furthermore, a slow rise in temperature during heating promoted increases of the grain size of CoO and Co and prevented the pulverization of Al. As a result, 75.5% of cobalt could be recovered from spent LIBs without contamination by aluminum.

DOI： 10.1252/kakoronbunshu.43.213

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Society of Powder Technology  

Smaller grinding media beads in bead mills are well known for determining high grinding performances. However, the post-grinding separation between beads and slurry might be a difficult task, especially in bead mills with centrifugal bead separation, where the separating performances are strongly affected by the shape of the rotors in the mill. Aiming to study and design grinding operations, the discrete element method (DEM) is a powerful tool which allows for predicting the grinding and separating performances in the mill. In this study, by using DEM simulations, we examined the slurry-beads separation in a bead mill and we investigated the influence of the rotor shape on the separating performances. We compared the performances of two kinds of rotors, one with conventional shape and one with outside projections for the activation of the media beads. Results of DEM simulation were in good agreement with experimental results.

DOI： 10.4164/sptj.54.377

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Hexavalent chromium (Cr(VI)) attracted researchers' interest for its toxicity, natural availability and removal difficulty. Nevertheless, its sorption mechanism is not clearly understood yet. In this work, we elucidated the sorption mechanism of the co-precipitation of chromates with ferrihydrite through quantitative analysis. The influence of Cr/Fe molar ratio on sorption was investigated by zeta potential measurements, X-ray diffraction (XRD) and X-ray adsorption fine-structure analysis (XAFS). Coprecipitation at pH 5 showed almost twice the sorption density of adsorption at pH 5. In co-precipitation, a shift of the XRD peak due to inner-sphere sorption of chromate was observed at Cr/Fe molar ratio 0.5. For adsorption, the same peak shift was confirmed at Cr/Fe molar ratio of 1. Zeta potential at pH 5 suggested that the sorption mechanism changed at Cr/Fe molar ratio 0.25 for coprecipitation and at Cr/Fe molar ratio of 1 for adsorption. Fitting of Cr and Fe K-edge extended X-ray adsorption fine-structure suggested that ferrihydrite immobilized Cr(VI) via outer sphere surface complexation for lower Cr/Fe ratios and via inner-sphere surface complexation for higher molar ratios. At higher molar ratios, bidentate binuclear Cr Fe bonds were well established, thus resulting in the expansion of the ferrihydrite structure. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jhazmat.2017.03.058

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

In this paper, LiCoO2/Li1.3Al0.3Ti1.7(PO4)(3) (LATP) composite granule as low-cost cathode for all-solid-state lithium-ion batteries was prepared by simple mechanical method using an attrition-type mill. LiCoO2 and LATP were chosen as the active material and the solid-state electrolyte, respectively. The mechanical treatment of LiCoO2 and LATP powders consisting of each nanoparticle provided the homogeneously dispersed composite granule with the granule size of several tens of micrometers. The all-solid-state lithium-ion battery fabricated from this composite granule exhibited the good electrochemical performances compared with that from the LiCoO2 granule without LATP. The capacity retention of approximate to 90% was obtained in the 20 cycles test. The inner dispersed LATP nanoparticles with a high conductivity of lithium ion played a crucial role in operating of the all-solid-state lithium-ion battery. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

DOI： 10.1016/j.apt.2015.10.013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

For the establishment of appropriate recycling process, the delamination of electric components from printed circuit boards (PCBs), which are major components of c-waste, is expected, because some of useful critical metals are concentrated in specific components. However, the knowledge about the mechanism of the delamination process in a drum typed agitation mill is still limited and uncertain. To better comprehend the mechanism, in this study, the particle-based simulation and comminution tests using handmade PCBs were conducted. The behavior of PCBs and the air flow in the mill having flexible chains was simulated by the discrete element method (DEM) coupled with computational fluid dynamics (CFD). To model the shape of PCBs, the particle based rigid body model was introduced into the DEM. Since this model could not directly simulate the breakage phenomena, collision energy was calculated to qualitatively evaluate the comminution performance. In addition, the simulation results were compared with the experimental comminution tests, This study demonstrated the behavior of PCBs and the air flow in the mill, and the effect of the air to comminution process in the mill. It was also shown that the collision energy related to parts collision was better correlated with the experimental results and this correlation can be assumed using first order rate equation, which suggested part detachment was mainly brought by direct collision to parts in the mill.

DOI： 10.2320/matertrans.M-M2016834

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Authorship：Lead author   Language：Japanese  

DOI： 10.7791/jspmee.5.358

CiNii Books

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DOI： 10.4164/sptj.52.634

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER CERAMIC SOC  

Carbon nanotubes (CNTs) are expected to be used to improve electrical conductivity and to reinforce mechanical properties of many materials. In our previous study, fabrication of CNT-dispersed S13N4 ceramics having high strength succeeded by uniform dispersion of CNTs using bead milling technique. However, their electrical conductivity degraded though the size of CNTs was not changed after bead milling process. The reason for the degradation is that formation of electrically conductive paths due to networking of CNTs was insufficient. In this study, networking of CNTs in ethanol was controlled by adding surfactant. Furthermore, CNT/alumina composites were fabricated by spark plasma sintering and their electrical and mechanical properties were evaluated. From optical microscopic observation, networking of CNTs in the slurry was occurred by adding ammonium polycarboxylate. Electrical conductivity of CNTs dispersed slurry increased with an increase in quantity of the added ammonium polycarboxylate and with an increase in the soaking time due to development of CNT network. Electrical conductivity of the CNT/alumina composites prepared by adding ammonium polycarboxylate were higher than those without ammonium polycarboxylate while having higher strength. The improvement of these properties resulted from homogeneous networking of CNTs formed by adding ammonium polycarboxylate to increase the conduction paths in the sintered body.

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Studies on the dispersion of carbon nanotubes (CNTs) in silicon nitride (Si3N4) ceramics to provide the latter with electrical conductivity have been carried out in recent years. The density and the strength of Si3N4 ceramics were degraded, however, because the CNTs prevented Si3N4 from densifying. The CNTs disappeared after firing at high temperatures owing to the reaction between CNTs and Si3N4 or SiO2, or both Si3N4 and SiO2. In order to improve the density and suppress the reaction, sintering aids for lower-temperature densification of Si3N4 are needed. In this study, we added HfO2 as a sintering aid to a Si3N4-Y2O3-Al2O3-AlN-TiO2 system to fabricate CNT-dispersed Si3N4 ceramics at lower temperatures. Furthermore, bead milling was applied to disperse the CNTs homogeneously. Agglomerates of CNTs were pulverized by bead milling without obvious changes in morphology to eliminate larger fracture origins in CNT-dispersed ceramics. As a result of both the addition of HfO2 and bead milling, we successfully fabricated dense CNT-dispersed Si3N4 ceramics with high strength and electrical conductivity. © 2014 The Ceramic Society of Japan and the Korean Ceramic Society.

DOI： 10.1016/j.jascer.2014.02.005

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Authorship：Lead author   Language：English   Publisher：The Materials Research Society of Japan  

The preparation of electrically conductive silicon nitride (Si₃N₄) ceramics by dispersing carbon nanotubes (CNTs) has been studied in the recent years. However, the density and strength of Si₃N₄ ceramics was found to deteriorate and the CNTs disappeared after firing at high temperatures because CNTs prevent Si₃N₄ from densification and there is a possibility that the CNTs reacted with the Si₃N₄ or SiO₂. To prevent the CNTs from reacting and disappearing, low temperature densification is required. In this study, HfO₂ was added to a Si₃N₄-Y₂O₃-Al₂O₃-AlN system to fabricate CNT-dispersed Si₃N₄ ceramics at low temperatures. As a result, a sample to which HfO₂ had been added and which was fired at lower temperatures showed higher electrical conductivity and higher bending strength. It was also observed that the mechanical and electrical properties of the ceramics depended on the quantity of added CNTs.

DOI： 10.14723/tmrsj.37.11

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Publishing type：Research paper (scientific journal)  

The study to give electrical conductivity by dispersing carbon nanotubes (CNT) into silicon nitride (Si 3N 4) ceramics has been carried out in recent years. However, the density and the strength of Si 3N 4 ceramics were degraded and CNTs disappeared after firing at high temperatures because CNTs prevent Si 3N 4 from densification and there is a possibility that CNTs react with Si 3N 4 or SiO 2. In order to suppress the reaction and the disappearance of CNTs, lower temperature densification is needed. In this study, HfO 2 and TiO 2 was added to Si 3N 4-Y 2O 3-Al 2O 3-AlN system to fabricate CNT-dispersed Si 3N 4 ceramics at lower temperatures. HfO 2 promotes the densification of Si 3N 4 and prevents CNT from disappearance. As a result, the sample by adding HfO 2 and TiO 2 fired at lower temperatures showed higher electrical conductivity and higher bending strength. It was also shown that the mechanical and electrical properties depended on the quantity of the added CNTs.

DOI： 10.4191/kcers.2012.49.4.333

Scopus

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Language：Japanese   Publisher：資源・素材学会  

CiNii Books

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