研究者詳細 - 山村　方人

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Migration of binder and conductive agent during drying process of Li-ion battery cathodes 査読有り国際誌

Kumano N., Yamaguchi Y., Akimoto Y., Ohshima A., Nakamura H., Yamamura M.

Journal of Power Sources 591 2024年01月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

Drying of an electrode film during a wet coating process for Li-ion batteries often leads to a heterogeneous distribution of the binder and conductive agent in the film thickness direction. Because this heterogeneous distribution affects battery performance and durability, understanding and controlling the migration behavior are important. Herein, the distribution of the components (active material/conductive agent/binder) of a cathode is investigated by a novel method and their relationship with the electrode properties is determined. The binder distribution is investigated via two methods: pyrolysis gas chromatography mass spectrometry (Py-GC/MS) analysis of cut electrodes, and low-voltage scanning electron microscopy with energy-dispersive X-ray spectroscopy. In the sample dried at 30 °C, more binder and conductive agent exists in the bottom layer. With increasing drying temperature, the binder and conductive agent migrate from the bottom to the surface because they are transported by capillary-driven convective flow through the pores between the active material particles. Drying at high temperatures causes migration, resulting in reduced adhesion between the electrode film and the current collector, and increases the electrode resistance. The Py-GC/MS method of characterizing the cut electrodes is shown to be a complementary method that can analyze a wider area than cross-sectional observation.

DOI： 10.1016/j.jpowsour.2023.233883

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Sigmoidal temporal increase in shear viscosity of titania–toluene–ethanol colloidal suspensions 査読有り国際誌

Yamamura M.

Colloids and Surfaces A: Physicochemical and Engineering Aspects 675 2023年10月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

The shear viscosity of toluene-based TiO2 nanoparticle/poly(vinyl acetate) suspensions initially increased gradually, then increased steeply, and finally levelled off under shearing in the presence of ethanol as a polar additive. This non-linear response followed a sigmoidal function with a characteristic rate constant for a given composition. The rate constant reached a maximum at a critical ethanol concentration, resulting in maxima of the final viscosity and storage modulus that have not been previously reported for non-aqueous macroscopically miscible systems. This viscosity anomaly was attributed to the preferential adsorption of the polar solvent and the resulting alcohol-clustering-induced particle networking in the non-polar medium. The temporal variations in viscosity were reproduced using a proposed kinetic model that newly considered inter-particle bonding assisted by ethanol adsorption. These results elucidate the transient rheological responses of suspensions containing polar/non-polar solvents for coating applications.

DOI： 10.1016/j.colsurfa.2023.132047

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Reaction-driven solvent transport in UV-curable phase-separating coatings 査読有り

Yamamura M.

Journal of Coatings Technology and Research 20 ( 1 ) 15 - 26 2022年01月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

We experimentally examined the time-evolutions of local compositions in photocurable, monomer-solvent-initiator ternary liquid film coatings using attenuated total-reflectance-Fourier transform infrared spectroscopy. The coatings exhibited phase separation upon UV exposure owing to the inherent partial miscibility between the solvent and the polymer. The solvent concentration at the bottom of the coating increased when exposed to UV light for 1 s from the top, showing a solvent transport along the irradiation direction. The differences in solvent concentration before and after UV exposure showed good agreement with model predictions based on stress-induced non-Fickian solvent mass transport. The solvent concentrations at the bottom remained constant in the case of discrete phase structures, whereas it exponentially decayed over time in bicontinuous phase structures. These results suggest that light-tunable microstructures enable the relaxation of the reaction-driven nonuniformity in solvent concentration distributions.

DOI： 10.1007/s11998-022-00661-7

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湿式塗布乾燥の基礎と粒子積層への課題

山村方人

粉体技術 14 15 - 19 2022年01月

Adsorption-mediated nonlinearity of critical cracking thickness in drying nanoparticle–polymer suspensions 査読有り

Yamamura M.

AIChE Journal 67 ( 5 ) 2021年05月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

We examine the critical cracking thicknesses of as-dried colloidal TiO2 suspensions containing water-soluble polymeric additives, above which cracks spontaneously propagate. In contrast to common observations, the critical cracking thickness increases in a nonlinear, stepwise manner as increasing the concentration of the polymeric additive in the suspension. The critical thickness diverges when the polymer content increases above a certain threshold. We demonstrate that the first and second critical cracking thickness increments are attributable to the onset of polymer adsorption and a subsequent transition in the conformations of the adsorbing polymer chains, respectively. The critical thickness profiles with respect to normalized polymer adsorption amounts at different particle diameters converged into a single master curve. These results illustrate nontrivial evaporation processes in which the various roles of polymeric additives delay cracking into thicker films.

DOI： 10.1002/aic.17229

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Drying paths of phase-separating solution coatings exposed to humidity 査読有り

Yamamura M.

Journal of Coatings Technology and Research 19 ( 1 ) 15 - 23 2021年01月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Drying process paths, i.e., time-dependent trajectories of solution compositions on a phase diagram, were examined for coatings of a water-immiscible acrylic monomer dissolved in ethanol and exposed to humidity. The absorption of water vapor quenched the solution into a thermodynamic nonequilibrium state and promoted a spontaneous phase separation when the water content in the solution exceeded a critical value. A simultaneous mass-loss and heat-flux measurement technique was proposed and adapted for phase-separating coatings to determine the evaporation rates of two volatile components with different latent heats of vaporization. The measured drying paths agreed with those predicted from a drying model that takes into account the gas-diffusion-limited evaporation and composition-dependent activities. The numerical predictions also revealed that the pseudo-azeotrope determined the critical drying conditions, under which any drying paths on the phase diagram did not cross the two-phase region, and thus the drying solutions remained stable.

DOI： 10.1007/s11998-021-00483-z

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液体薄膜コーティングと乾燥：欠陥形成に与えるレオロジー特性の影響招待有り査読有り

山村方人

色材協会誌 ( 一般社団法人色材協会 ) 93 ( 1 ) 23 - 27 2020年01月

担当区分：筆頭著者記述言語：日本語掲載種別：記事・総説・解説・論説等（学術雑誌）

液体フィルムの塗布乾燥は，さまざまな先端材料プロセスに対する共通基盤技術の一つである。粒子分散液，コロイド，ゲルなどのソフトマターから均一なフィルムを得るには，望ましくない塗布乾燥欠陥の形成メカニズムと，塗布液のレオロジー特性との間の相関関係を理解することが大切である。そこで本稿では，産業で用いられる代表的な方式の一つであるスロットダイ塗布を取り上げ，欠陥形成を抑制しプロセスの生産性を向上させるために必要な液物性の考え方について紹介する。

DOI： 10.4011/shikizai.93.23

その他リンク： https://ci.nii.ac.jp/naid/130007790904

Ribbing instability of Newtonian fluid coated on a topographic surface 査読有り

Yamamura M.

Journal of Coatings Technology and Research 17 ( 6 ) 1447 - 1453 2020年01月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2020, American Coatings Association. Periodic wavy patterns emerge and align in a transverse direction once a viscous fluid is coated onto a surface moving above a critical speed. In this study, we examine how this flow instability, which is usually referred to as ribbing, is triggered or damped on a moving topographic surface. To examine the transient flow behavior, the liquid first came into contact with a smooth surface, followed by a downstream surface with small-scale V-shaped grooves. Flow visualizations revealed a topography-induced flow stabilization and a matching of rib frequencies with the underlying groove patterns, depending on the groove geometry and capillary number.

DOI： 10.1007/s11998-020-00375-8

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Phase separation fundamentals-toward applications of particle assembly- 招待有り査読有り

Yamamura M.

Journal of the Society of Powder Technology, Japan ( 一般社団法人粉体工学会 ) 57 ( 3 ) 130 - 136 2020年01月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2020 Society of Powder Technology. All rights reserved. This article provides a brief overview of liquid-liquid phase separation fundamentals. First we discuss thermodynamic factors that drive spontaneous phase separation from homogeneous binary liquid mixtures. Next we introduce some mathematical models for chemical potentials in non-equilibrium state and intermolecular frictions to derive the governing equation for phase separations. Following classical Cahn-Hilliard theory, we show how the linear stability analysis gives the critical wavelength, at which the growth rate of concentration fluctuation shows a maximum. Finally, we discuss possibilities to utilize phase separation structures as a template to assemble/deposit/stratify solid particles on a solid surface.

DOI： 10.4164/sptj.57.130

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九州工業大学工学部応用化学科の化学実験教育査読有り

中戸晃之, 竹中繁織, 岡内辰夫, 山村方人, 植田和茂

化学と教育 ( 公益社団法人日本化学会 ) 68 ( 3 ) 114 - 117 2020年01月

記述言語：日本語掲載種別：記事・総説・解説・論説等（学術雑誌）

九州工業大学工学部応用化学科では，2年次前期より3年次後期にかけて，分析化学，物理化学，有機化学，化学工学・無機化学の順序で，学生実験を実施している。実験技術の習得に加え，エンジニアリングデザイン，コミュニケーション，チームワークなどの能力の涵養も目的としている。有機化学実験ではPBL（課題解決型学習）方式を取り入れており，学生アンケートや教員の実感では有効に機能していると考えられる。

DOI： 10.20665/kakyoshi.68.3_114

その他リンク： https://ci.nii.ac.jp/naid/130007993107

Formation mechanism of asymmetric porous polymer films by photoinduced phase separation in the presence of solvent 査読有り

Yoshihara H., Yamamura M.

Journal of Applied Polymer Science 136 ( 34 ) 2019年09月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2019 Wiley Periodicals, Inc. Photoinduced phase separation in the presence of a nonreactive volatile solvent provides a simple, light-tunable, and cost-effective route for fabrications of porous polymer films. Here, we show that the short-time (<10 s) ultraviolet irradiation of a photoreactive solution film promotes particular asymmetries in the composition and porosity across the thickness. Confocal Raman spectroscopy revealed that the compositional asymmetry is maximum at a certain critical light intensity. We discuss the film formation mechanism based on the light-driven diffusion of the solvent and monomer. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47867.

DOI： 10.1002/app.47867

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Concentration profiles in phase-separating photocuring coatings 査読有り

Yoshihara H., Yamamura M.

Journal of Coatings Technology and Research 16 ( 6 ) 1629 - 1636 2019年01月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2019, American Coatings Association. We directly measured the local composition profiles in phase-separating photocurable thin films using confocal Raman spectroscopy. To avoid light scattering at phase interfaces, we developed a novel technique to replace the solvent with a monomer to match the reflective indices in the cured films. The results indicated that the concentration distribution of the polymer was uniform in solvent-free monomer/initiator binary solutions, while it was spatially nonuniform when the solvent-based films were thermodynamically unstable and promoted reaction-induced phase separation upon UV irradiation on the top surface. In the latter case, the film exhibited a dual-layer structure, in which the polymer concentration was almost uniform near the top surface, while concentration gradients developed near the bottom surface. The thickness of the top layer with a uniform concentration profile increased with the increase in the UV light intensity. These results implied that the propagation of the reaction front and the resulting light-driven transport of the solvent toward the bottom coating layer played key roles in the formation of nonuniform concentration profiles in photocuring solution coatings.

DOI： 10.1007/s11998-019-00216-3

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ウェット塗布膜乾燥過程の評価技術招待有り

山村方人, 吉原宏和

日本印刷学会誌 ( 社団法人日本印刷学会 ) 56 ( 2 ) 85 - 88 2019年01月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

In this article, we attempt to provide a brief guide to the recent progress in experimental techniques to monitor the transient drying process of multicomponent thin liquid film coatings. First, we report simultaneous measurements of the heat-fluxes and masses of coatings, which allow us to determine the drying rates of two different solvents as a function of the drying time. Second, we demonstrate that, in drying suspensions that contain particles of varying sizes, the photo-luminescence measurement in the course of drying is a powerful tool for capturing the migration of small particles to the top surface. However, the depth-concentration profiles of the particles are not directly determined by this technique. As an alternative tool to capture the concentration distributions in a drying coating, we introduce confocal Raman spectroscopy and reportits recent application in phase-separating polymeric coatings by utilizing a novel solvent-replacement technique. Finally, we reporton a cantilever beam-deflection technique to measure the stress developments in a drying coating. A combination of these techniques may provide a new horizon toward a fundamental understanding of the microstructural development of drying multicomponent films.

DOI： 10.11413/nig.56.85

その他リンク： https://ci.nii.ac.jp/naid/130007649790

グラビアロール塗布の流体力学招待有り

山村方人, 三浦秀宣

表面技術 ( 一般社団法人表面技術協会 ) 69 ( 7 ) 265 - 268 2018年01月

ウェットコーティングの基礎招待有り

山村方人

成形加工 ( 一般社団法人プラスチック成形加工学会 ) 30 ( 12 ) 606 - 609 2018年01月

Two-step migration of particles in evaporating bimodal suspension films at high Peclet numbers 査読有り

Tashima T., Yamamura M.

Journal of Coatings Technology Research 14 ( 5 ) 965 - 970 2017年09月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017, American Coatings Association. During the drying of bimodal colloidal suspensions containing particles of various sizes, smaller particles preferentially migrate to the top surface under particular drying conditions, leading to undesirable drying defects in batteries and in other coating applications. Despite extensive previous studies, the migration mechanism is far from being understood because few in situ observations are available to support the hypotheses. To remedy this, we use real-time photoluminescence (PL) microscopy to investigate the migration of small fluorescent latex particles co-dispersing with large nonemissive latex particles. Comparing the measured PL intensity with that predicted by a model allows us to determine the quantity of small particles near the evaporating surface. The results reveal that the fluorescent particles segregate in two steps: The primary segregation occurs early in the evaporation stage, whereas the secondary stepwise migration occurs when the air–liquid interface invades the particle consolidation layer. The latter migration is attributed to the flow-induced motion of small particles that move through interstitial spaces between large particles.

DOI： 10.1007/s11998-017-9946-1

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化学工学教育における情報技術の活用に関するアンケート報告

山村方人

化学工学 ( 化学工学会 ) 81 ( 2 ) 93 - 95 2017年02月

粒子分散膜の塗布乾燥技術

山村方人

粉体技術 ( 日本粉体工業技術協会 ) 9 ( 2 ) 133 - 139 2017年02月

A critical condition for overfill-to-starve transition of doctor-bladed liquids in gravure coatings 査読有り

Miura H., Miura H., Tsuruoka A., Yamamura M.

Journal of Chemical Engineering of Japan ( 公益社団法人化学工学会 ) 50 ( 4 ) 262 - 267 2017年01月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Copyright © 2017 The Society of Chemical Engineers, Japan.The present study measured free surface profiles of doctor-bladed fluids on engraved roll surface in order to quantify the volumes of fluid retained in tri-helical grooves. The fluid overfilled the grooves to cover the entire surface of the roll at low roll speeds; whereas, it exhibits a concave surface profile in each groove at high speeds, i.e. a starved configuration with a partial filling of the groove. The overfill-to-starve transition was observed with decreasing the static liquid pressure and the depth-to-width aspect ratio of grooves, or increasing the blade thickness and the fluid viscosity. The dimensionless volumes of residue on the roll obeyed a master curve with respect to a balance between the pressure-driven and viscous drag flows. An empirical equation was newly derived based on the one-dimensional lubrication approximation, which allowed us to predict an optimum condition in stable gravure coating operations.

DOI： 10.1252/jcej.16we291