研究者詳細 - 市野　良一

論文 - 市野　良一

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Room-Temperature Bulk Supramolecular Polymer Based on C<inf>3</inf>-Symmetrical Benzene-1,3,5-tricarboxamides Having Two-Armed Alkyl Groups as Side Chains 査読有り国際誌

Ishigaki Y., Yamanaka M., Hagio T., Ichino R.

ChemistrySelect 8 巻 ( 35 ) 2023年9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）出版者・発行元：ChemistrySelect

To develop a bulk supramolecular polymer based on 1,3,5-benzenetricarboxamide (BTA) without crystallinity at room temperature, C3-synmetrical BTA derivatives with two-armed alkyl groups were synthesized and characterized. IR and XRD measurements of the BTA derivatives suggested that the higher-order structure obtained using these materials was hexagonal columnar, owing to the characteristic three-fold hydrogen bonding. In DSC measurements, BTA having 10-nonadecyl groups (10NDBTA) showed only a single transition point at 233 °C and maintained its mesophase down to −50 °C, whereas the other BTA derivatives showed a transition peak in the range of 20 to 131 °C and another in the range of 204 to 239 °C, corresponding to alkyl melting and dissociation of the stacked BTA cores, respectively. 13C-SSNMR measurement of 10NDBTA indicated that not only the 10-nonadecyl groups of the side chains but also the BTA cores forming the main chain of the supramolecular polymer show a unique high mobility even at ambient temperature.

DOI： 10.1002/slct.202300805

Utilization of agricultural waste to herbicide removal: Magnetic BEA zeolite adsorbents prepared by dry-gel conversion using rice husk ash–derived SiO<inf>2</inf> for paraquat removal 査読有り国際共著国際誌

Phouthavong V., Hagio T., Park J.H., Nijpanich S., Srihirunthanon T., Chantanurak N., Duangkhai K., Rujiravanit R., Chounlamany V., Phomkeona K., Kong L., Li L., Ichino R.

Arabian Journal of Chemistry 16 巻 ( 8 ) 2023年8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）出版者・発行元：Arabian Journal of Chemistry

This study presents a method that will allow for the sustainable utilization of rice husk ash-SiO2 (RHAS), an agricultural-waste–derived material, as a bulky solid SiO2 source in the zeolite beta (BEA)/Fe3O4 composite (magnetic RHAS-BEA) synthesis via a dry-gel conversion method for the removal of paraquat, a typical herbicide, from aqueous solutions. Ultrasonic waves were used to facilitate the formation of uniform Fe3O4-contained dry precursor gel before converting to the magnetic BEA zeolite composite for the first time. Magnetic RHAS-BEA was then characterized and compared with a non-magnetic sample (RHAS-BEA) using X-ray diffraction and field-emission scanning electron microscopy. In terms of adsorption, we found that paraquat had a high adsorption rate on the samples and conformed to a pseudo-second-order kinetic model. The adsorption behavior of paraquat on the synthesized RHAS-BEA and magnetic RHAS-BEA obeyed the Langmuir adsorption isotherm model. The synthesized adsorbents were reusable for at least four cycles, via thermal regeneration at 450 °C. The inclusion of Fe3O4 particles in magnetic RHAS-BEA disrupted neither the crystallization of the BEA zeolite nor the adsorption of paraquat and enabled easy collection via an external magnet.

DOI： 10.1016/j.arabjc.2023.104959

An effective strategy for improving the performance of electrodeposited Fe-W alloy plating: Tailoring microstructure by graphene incorporation 査読有り国際共著国際誌

Shinohara Y., Park J.H., Hagio T., Kim J.I., Lee W.Y., Umehara N., Ichino R.

Materials and Design 230 巻 2023年6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）出版者・発行元：Materials and Design

Despite the excellent performance of hard Cr plating using hexavalent chromium (Cr6+), its use is being restricted owing to recent environmental regulations. Electrodeposited Fe-W alloy is considered a possible alternative, but its high coefficient of friction (COF), high wear rate owing to tribo-oxidation, and high corrosion rate hinder its practical application. In this study, we attempted to solve these problems by modifying the microstructure of Fe-W alloy by incorporating 2D-structured graphene. The effect of graphene incorporation on the structure of the Fe-W alloy and its properties, especially microhardness, wear, and corrosion resistance, were investigated. The results showed the graphene effectively modified the columnar structure of the Fe-W alloy by inhibiting the vertical growth of clusters during electrodeposition, leading to fragmentation of the vertical cluster boundaries. This improved the hardness by as much as 17 % up to 9.1 GPa, and the corrosion resistance by changing the corrosion mechanism from localized corrosion to uniform corrosion. In addition, the graphene reduced the COF and wear rate by reducing the Fe2O3 formed by tribo-oxidation to a lower oxidation state. The structural modification of the plating by graphene incorporation thus provides an effective solution to improving the performance of Fe-W alloys.

DOI： 10.1016/j.matdes.2023.111938

Preliminary Study on Electrodeposition of Copper Platings and Codeposition of Carbon Nanotubes from Organic Solvent 査読有り国際誌

Park J.H., Fujita Y., Hagio T., Phouthavong V., Kamimoto Y., Bessho T., Ichino R.

Coatings 13 巻 ( 4 ) 2023年4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）出版者・発行元：Coatings

Metal/carbon composite plating is an effective strategy for improving and adding properties to metal plating by incorporating carbon materials into the metal matrices. Copper (Cu) is widely applied, particularly in the areas of heat management and electronic packaging owing to its high thermal and electrical conductivities, which can be further improved together with improvements in mechanical properties by compositing it with carbon nanotubes (CNTs). However, because hydrophobic CNTs are hardly dispersible in aqueous solutions, additional intense acid treatment or the addition of dispersants is required for their dispersion. Moreover, previous studies have reported that these methods suffer from deterioration of composite material performance through the destruction of the CNT surface or the inclusion of dispersants into the plating. Therefore, in this study, the electrodeposition of a Cu/CNT composite in a non-aqueous solvent that can disperse CNTs without any additional treatment is investigated. The experimental results show that it is possible to deposit Cu from a N-methyl-2-pyrrolidone containing copper iodide and potassium iodide. Furthermore, Cu/CNT composite platings containing CNTs up to 0.12 mass% were prepared by constant current electrolysis, and applying pulse electrolysis can increase the CNTs content up to 0.22 mass%.

DOI： 10.3390/coatings13040802

Magnetic Adsorbents for Wastewater Treatment: Advancements in Their Synthesis Methods 査読有り国際共著国際誌

Phouthavong V., Yan R., Nijpanich S., Hagio T., Ichino R., Kong L., Li L.

Materials 15 巻 ( 3 ) 2022年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials

The remediation of water streams, polluted by various substances, is important for realizing a sustainable future. Magnetic adsorbents are promising materials for wastewater treatment. Although numerous techniques have been developed for the preparation of magnetic adsorbents, with effective adsorption performance, reviews that focus on the synthesis methods of magnetic adsorbents for wastewater treatment and their material structures have not been reported. In this review, advancements in the synthesis methods of magnetic adsorbents for the removal of substances from water streams has been comprehensively summarized and discussed. Generally, the synthesis methods are categorized into five groups, as follows: direct use of magnetic particles as adsorbents, attachment of pre-prepared adsorbents and pre-prepared magnetic particles, synthesis of magnetic particles on pre-prepared adsorbents, synthesis of adsorbents on preprepared magnetic particles, and co-synthesis of adsorbents and magnetic particles. The main improvements in the advanced methods involved making the conventional synthesis a less energy intensive, more efficient, and simpler process, while maintaining or increasing the adsorption performance. The key challenges, such as the enhancement of the adsorption performance of materials and the design of sophisticated material structures, are discussed as well.

DOI： 10.3390/ma15031053

Nano ferric oxide adsorbents with self-acidification effect for efficient adsorption of Sb(V) 査読有り国際共著国際誌

Feng X., Yan R., Zhang Q., Wan Q., Hagio T., Ichino R., Kong L., Cao X., Li L.

Chemosphere 272 巻頁： 129933 2021年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Chemosphere

It is urgent and essential to remove antimony from wastewater due to its potential carcinogenicity. In this paper, a nano ferric oxide (NFO) adsorbent was synthesized in a one-step low temperature calcination (150 °C) process. It presents a surprising self-acidification behavior, could automatically adjust the pH to around 4 from different intimal pH values (4–9), which enable it to efficiently remove more than 99% of Sb(V) from wastewater in a wide pH range. X-ray photoelectron spectroscopy analysis proved that the self-acidification function was originated from the hydrolyzation of surface Fe atoms on ferric oxide nanoparticles. The maximum adsorption capacity of this adsorbent is 78.1 mg/g which is 2–3 times higher than that of the samples obtained at higher temperatures (250 °C and 350 °C), and also its adsorption kinetic constant is ten times higher, which can be attributed to the larger surface areas and smaller sizes of ferric oxides synthesized at 150 °C. In the actual wastewater treatment, the effluent's concentration after treatment can be maintained below the instrument detection limit even under low initial antimony concentration. We believe that this new adsorbent has great potential in the practical application in the treatment of Sb polluted wastewaters due to its simple synthesis, high efficiency, and low cost.

DOI： 10.1016/j.chemosphere.2021.129933

Facile Hydrothermal Synthesis of EAB-Type Zeolite under Static Synthesis Conditions 査読有り国際共著国際誌

Hagio T., Park J.H., Lin Y., Tian Y., Hu Y.H., Li X., Kamimoto Y., Ichino R.

Crystal Research and Technology 56 巻 ( 4 ) 2021年4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）出版者・発行元：Crystal Research and Technology

Conventionally, EAB-type zeolites are crystallized by hydrothermal synthesis for many days under agitational synthesis conditions such as rotation or stirring. In the present study, EAB-type zeolite is obtained by hydrothermal synthesis within 12 h under static synthesis conditions for the first time. The effects of crystallization temperature, aging of the precursor sol, and addition of seed crystals are investigated. The results reveal that EAB-type zeolite can be obtained when using a precursor sol with short aging time followed by hydrothermal synthesis in a very narrow temperature range 110 °C−120 °C under static synthesis condition. Addition of seed crystals is found to suppress the formation of SOD-type zeolite, the primary phase at high hydrothermal synthesis temperatures, while it does not increase the crystallization rate of EAB-type zeolite. Furthermore, the crystallization behavior at 120 °C is examined by varying the synthesis time. EAB-type zeolite with invariably twinned plate-like morphology starts to crystallize between synthesis time of 3 to 6 h at 120 °C under the static synthesis condition.

DOI： 10.1002/crat.202000163

Development of novel nanoporous hexagonal tungsten oxide membrane for separation of water/acetic acid mixtures via pervaporation 査読有り国際誌

Kunishi H., Hagio T., Wada S., Kamimoto Y., Ichino R.

Journal of Membrane Science 620 巻 2021年2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）出版者・発行元：Journal of Membrane Science

A novel nanoporous hexagonal tungsten oxide (NP-h-WO3) membrane was developed for separating water/acetic acid (H2O/AcOH) mixtures. The nanopores on the c-plane of h-WO3 are larger than H2O molecules and smaller than AcOH molecules and thus should allow for their effective separation. Moreover, h-WO3 exhibits high stability in acids (pH < 4). Therefore, c-axis-aligned NP-h-WO3 membranes are promising for the separation of H2O/AcOH mixtures. Given this background, we report, for the first time, the synthesis of c-plane-aligned dense NP-h-WO3 membranes on porous ceramic supports via the hydrothermal method using a precursor solution containing AcOH. The presence of AcOH and the concentration of Na2WO4 in the precursor solution are the key factors affecting crystal growth and alignment along the c-plane. A high Na2WO4 concentration is necessary for obtaining membranes with a high degree of c-plane alignment. Thus, dense, c-plane-aligned NP-h-WO3 membranes could be fabricated by precoating the support with amorphous WO3 seeds and subsequent hydrothermal synthesis in a precursor solution of Na2O/WO3/AcOH/H2O (1/1/0.88/201) at 180 °C for 24 h. The fabricated membranes exhibited a maximum separation factor of 42.6 during the pervaporation of a H2O/AcOH mixture (10/90 (w/w)) at 80 °C. Thus, these NP-h-WO3 membranes are highly suited for H2O/AcOH separation.

DOI： 10.1016/j.memsci.2020.118860

Synthesis of C-plane oriented hexagonal tungsten oxide membranes on tubular substrates and their acetic acid/water separation performances 査読有り国際共著国際誌

Kunishi H., Wada S., Kamimoto Y., Ichino R., Lin Y., Kong L., Li L., Hagio T.

Membranes 11 巻 ( 1 ) 頁： 1 - 17 2021年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Membranes

Hexagonal tungsten oxide (h-WO3) membrane is a novel candidate for dehydration of acetic acid (CH3COOH)/water mixtures owing to its molecular sieving property and acidic resistance. Meanwhile, c-plane orientation is an important factor for h-WO3 membranes because the pores of h-WO3 run along its c-axis. However, so far, high c-plane orientation has not been successful on tubular substrates. Here, the effect of synthesis conditions of h-WO3 membranes on tubular substrates against c-plane orientation and CH3COOH/water separation performance are investigated. The h-WO3 membranes were prepared by hydrothermal synthesis from a precursor sol containing various amounts of sodium tungstate (Na2WO4) in the presence of tubular substrates with seeds embedded on their outside surface. The seeding method and the amount of Na2WO4 in the precursor sol significantly affected both crystal orientation and densification of the membrane. A precursor sol with appropriate amounts of Na2WO4 was essential to simultaneously satisfy high c-plane orientation and densification of the membrane while excess Na2WO4 drastically decreased the degree of c-plane orientation. A highly c-plane oriented h-WO3 membrane was successfully obtained under the optimized condition, which exhibited a maximum separation factor of 40.0 and a water permeance of 1.53 × 10−7 mol·m−2·s−1·Pa−1 in a 90:10 wt % CH3COOH/water mixture. The water permeance approximately doubled compared to the previous report, possibly owing to the significantly higher degree of c-plane orientation. Furthermore, it was found that its separation ability can be maintained while stored in 90:10 wt % CH3COOH/water mixture with pH < 0 for more than 500 h.

DOI： 10.3390/membranes11010038

Electrodeposition of nano-diamond/copper composite platings: Improved interfacial adhesion between diamond and copper via formation of silicon carbide on diamond surface 査読有り国際誌

Hagio T., Park J.H., Naruse Y., Goto Y., Kamimoto Y., Ichino R., Bessho T.

Surface and Coatings Technology 403 巻 2020年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Surface and Coatings Technology

Although copper is an effective heat-dissipation material, a material with a higher thermal conductivity is required to meet the demands of future electronics. Carbon materials (CMs) are of great interest owing to their excellent thermal conductivities; however, it is difficult to apply CMs individually because of their brittleness and low formability. CM/copper composites are expected to overcome these drawbacks. Diamond is of special interest for preparing composites because they do not require control of orientation owing to their isotropic thermal conductivity, but unfortunately, diamond and copper generally show poor interfacial adhesion. Therefore, designing an interface to improve their adhesion is essential to realizing high thermal conductivity. In this study, SiC-coated diamonds were adopted to fabricate diamond/copper composite platings by electrodeposition for the first time. Electrodeposition was carried out in a copper sulfate bath containing pristine and SiC-coated diamonds. The formation of SiC slightly decreased the current efficiency but did not significantly affect the diamond content of the plating. The sample with the nano-diamond/copper composite plating containing 1.07 mass% (2.72 vol%) of SiC-coated nano-diamonds exhibited a thermal conductivity 46 Wm−1 K−1 higher than that of the sample with pure copper plating. From observations of the diamond/copper interface using micron-sized diamonds as a model, an obvious gap was observed between the diamonds and the copper when using pristine diamonds, whereas no gaps were observed when using the SiC-coated diamonds. SiC formation significantly improved the adhesion between the diamonds and copper. In addition, copper was directly deposited onto the surfaces of the SiC-coated diamonds in contrast to pristine diamonds, which showed no sign of deposition.

DOI： 10.1016/j.surfcoat.2020.126322

Electrodeposition of a novel ternary fe⇓w⇓zn alloy: tuning corrosion properties of fe–W based alloys by zn addition 査読有り国際誌

Park J.H., Hagio T., Kamimoto Y., Ichino R.

Journal of the Electrochemical Society 167 巻 ( 13 ) 2020年10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）出版者・発行元：Journal of the Electrochemical Society

Herein, we report the electrodeposition of a novel ternary Fe–W–Zn alloy. Ternary alloys with compositions of Fe–(29.08–35.96 at.%) W–(1.73–8.16 at.%) Zn were prepared by potentiostatic deposition in citrate–ammonia aqueous solution equipped with an anode chamber. The electrodeposition behavior of the ternary Fe–W–Zn alloys and the effect of the Zn addition were analyzed by cyclic voltammetry and in situ electrochemical quartz crystal microbalance measurements. Ternary alloys with glossy appearances and smooth surface morphologies were fabricated, with a maximum current efficiency of approximately 43%. Incorporating Zn into the Fe–W alloy structure transformed the alloy structure into an amorphous-like nanocrystalline structure and refined the crystal size to a minimum of 1.45 nm. Potentiodynamic polarization test results showed that the corrosion resistance of the ternary Fe–W–Zn alloy with approximately 2 at.% Zn was distinctly improved compared to the binary Fe–W alloy, both in 1 M H2SO4 solution and neutral 3 mass% NaCl solution. Notably, the corrosion resistance was even better than Ni–W alloy in 1 M H2SO4 solution, with its unique passivation behavior. The incorporation of Zn was found to be effective for tuning the corrosion properties of Fe–W alloys.

DOI： 10.1149/1945-7111/abbe59

Rapid determination of iron concentration in wastewater using color band formation 査読有り国際誌

Imai R., Kamimoto Y., Hagio T., Jung Y.J., Ichino R.

SN Applied Sciences 2 巻 ( 9 ) 2020年9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）出版者・発行元：SN Applied Sciences

High concentrations of iron ions in water bodies cause odour and discolouration due to their precipitation. The total iron ion concentration is generally analysed on-site by forming coloured compounds and measuring colour intensity with spectrophotometric or visual analysis. In this work, we developed a detection tube as an alternative simple analytical method, where the total iron ion concentration is measured not by colour but by an objective parameter called the colour band length (CBL). Tiron was selected as the colouring agent since it oxidises divalent iron ions into a trivalent state and reacts with trivalent iron ions to form a 3:1 anion complex in alkaline media, giving a red colour. The coloured solution penetrates the detection tube by capillarity, and the colour band is formed by the entrapment of the hydrophobic ion pair of iron-tiron complex and quaternary ammonium ions of the adsorbent filled in the tube. The CBL was found to correlate well with the total iron ion concentration quantitatively under the optimized measurement condition, and 5 to 40 mg-FeL−1 solutions could be measured with good objectivity and precision.

DOI： 10.1007/s42452-020-03331-8

Improvement in corrosion resistance of ternary Zn-Fe-Mo plating by additional Mo-oxide coating 査読有り国際共著国際誌

Park J.H., Kosugi D., Hagio T., Kamimoto Y., Ichino R., Lee M.H.

Surface and Coatings Technology 389 巻 2020年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Surface and Coatings Technology

Despite the excellent corrosion resistance and the widespread application of Zn-Ni plating in industrial fields, the toxicity of Ni to the human body has caused the demand for alternative plating that does not contain harmful elements. In this respect, ternary Zn-Fe-Mo plating, which includes a third element Mo in binary Zn-Fe plating, has been considered as a promising alternative for Zn-Ni plating. In this study, the corrosion resistance of ternary Zn-Fe-Mo plating was evaluated and compared with conventional Zn and Zn-Fe plating by impedance measurements and cyclic corrosion tests (CCT). Furthermore, formation of a multi-layer structure via additional Mo-oxide coating over the ternary Zn-Fe-Mo plating was attempted to increase the corrosion resistance. Experimental results show that ternary Zn-Fe-Mo plating has higher impedance but lower corrosion resistance for CCT and that the Mo-oxide coating significantly enhances the corrosion resistance of the ternary Zn-Fe-Mo plating selectively by a factor of approximately 10. The role of the formation of multi-layer structure in improving the corrosion resistance of the ternary Zn-Fe-Mo plating is discussed through the structure change of the plating and the generated corrosion products.

DOI： 10.1016/j.surfcoat.2020.125567

Selective recovery of indium via continuous counter-current foam separation from sulfuric acid solutions II – Optimization of operational parameters on separation performance 査読有り国際誌

Kinoshita T., Ishigaki Y., Kitagawa S., Ichino R., Kamimoto Y.

Separation and Purification Technology 238 巻 2020年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Separation and Purification Technology

Continuous counter-current foam separation under the simultaneous injections of metal and surfactant solutions into rising foam bed was applied to recover In(III) from a sulfuric acid solution. In this system, an anionic organophosphate surfactant containing a similar structure to a phosphoric acid extractant, D2EHPA, was employed as the metal collector with addition of a nonionic co-surfactant as a foam stabilizer. Among the various commercial products available, A219B/POOE20 was elucidated as the optimum combination of anionic/nonionic surfactants. In this study, the effects of the experimental parameters such as the aqueous pH, air flow rate, and injection rates of metal and surfactant solutions were discussed in terms of the percent recovery and separation factors of In(III) over the other metals. The results were successfully obtained under the optimized conditions with a dose of ascorbic acid as a reductant for Fe(III); the percent recoveries of indium and iron; the separation factors of In/Fe, In/Cu, and In/Zn; and the enrichment ratio of indium were 97%, 1.1%, 93, 1300, 1300, and 5.5, respectively. The mixture mol ratio of mono- and di-esters of anionic A219B was derived as 35:65 by a slope analysis, and the mono-esters would influence the separation performance in the case of rich A219B concentration in foam bed. The performance comparison of this method with solvent extraction using D2EHPA or the conventional foam separation was also presented.

DOI： 10.1016/j.seppur.2019.116490

Development of Synthetic Magnetic Zeolite Adsorbents and Application to Ammonium Ion Removal 査読有り国際共著国際誌

Kamimoto Y., Hagio T., Jung Y.J., Ichino R., Gil K.

KSCE Journal of Civil Engineering 24 巻 ( 5 ) 頁： 1395 - 1399 2020年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：KSCE Journal of Civil Engineering

Synthetic magnetic zeolite with Fe3O4 was developed and its adsorption performance of ammonium ions was examined. The influence of pH levels, Fe3O4 content of the magnetic zeolite, magnetization curve of the magnetic zeolite and isotherm curve were examined in batch type experiments. Magnetic zeolite synthesized by a hydrothermal process was observed with less than 12.6 wt% of Fe3O4 content by scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. With the optimum pH level around 8, qe decreases linearly with the increase of Fe3O4 content. Additionally, the adsorption isotherm of ammonium ions is approximated by a Langmuir equation when the maximum adsorption was obtained at about 1.60 mmolg−1. Such processes as the substitution and thermal desorption methods were successfully introduced to regenerate the magnetic zeolite saturated by ammonium ions, which is shown to be easily separated by magnetic force. Thus, the magnetic zeolite is a potential adsorbent for the removal of ammonium ions with an easy separation method using a magnetic process.

DOI： 10.1007/s12205-020-2185-5

Enhancement of corrosion resistance by lamination of Mg film on Zn-55Al-1.6Si-coated steel by physical vapor deposition 査読有り国際共著国際誌

Park J.H., Hagio T., Kamimoto Y., Ichino R., Lee M.H.

Surface and Coatings Technology 387 巻 2020年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Surface and Coatings Technology

Pure Mg films are laminated on hot-dip Zn-55Al-1.6Si-coated steel by physical vapor deposition. Ar gas pressure and deposition time are varied to control the crystal alignment and thickness of the Mg films. Potentiodynamic polarization tests, neutral salt spray tests (SST) and cyclic corrosion tests (CCT) are employed to evaluate the corrosion resistances of Mg laminated Zn-55Al-1.6Si-coated steel. The results show that lamination of Mg films enhance the corrosion resistance, especially against the cross-section by a factor of 2 to 10. The corrosion resistance is significantly affected by Mg film thickness. Polarization test results indicate that corrosion resistance of Mg films is slightly improved by crystal alignment against (101) plane. The effects of Mg films on corrosion process of Zn-55Al-1.6Si-coated steel are investigated via analysis of corrosion products formed during the SST and CCT. Lamination of Mg films seem to hinder the corrosion process by cathodic protection and formation of protective Mg corrosion products at defective areas through Mg ion migration while the underlying Zn-55Al-1.6Si coating protects steel substrate surface. The improvement in corrosion resistance under different corrosion environments of SST and CCT is explained by the transformation of Mg corrosion products from magnesium hydroxide to a more protective hydromagnesite.

DOI： 10.1016/j.surfcoat.2020.125537

Magnetic BEA-type zeolites: preparation by dry-gel conversion method and assessment of dye removal performance 査読有り国際共著国際誌

Phouthavong V., Hiraiwa M., Hagio T., Nijpanich S., Chounlamany V., Nishihama T., Kamimoto Y., Ichino R.

Journal of Material Cycles and Waste Management 22 巻 ( 2 ) 頁： 375 - 382 2020年3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）出版者・発行元：Journal of Material Cycles and Waste Management

The large pores and the rather hydrophobic nature of silica-rich BEA-type zeolites make them promising dye adsorbents. Composites of such zeolites and magnetic particles (magnetic zeolites), commonly prepared using hydrothermal techniques, can be rapidly and reliably removed from treated wastewater through magnetic separation and are therefore more practical than conventional zeolites. However, the incorporation of magnetic particles is difficult to control since it depends greatly on whether the zeolite nucleation occurs in the vicinity of magnetic particles or not. To overcome this problem, we herein synthesize silica-rich magnetic BEA-type zeolites via a different route called dry-gel conversion, namely by exposing a precursor gel containing well-dispersed magnetite to water vapor at 180 °C for 12 h. The obtained samples were characterized by XRD and SEM–EDS and their dye adsorption performance were evaluated using methylene blue as a model. The results indicate that the precursor gel was successfully converted into BEA-type zeolites that contain homogeneously distributed magnetite, exhibit a high methylene blue adsorption capacity (133 mg/g), and can be easily separated by application of a magnetic field. Consequently, this study paves the way to the development of an efficient wastewater treatment technology and thus contributes to the establishment of a green society.

DOI： 10.1007/s10163-020-00994-8

Electrochemical behavior of tungsten carbide-cobalt alloy using molten hydroxide as electrolyte under low temperature 査読有り国際共著国際誌

Kamimoto Y., Kasuga R., Takeshita K., Hagio T., Kuroda K., Ichino R., Deevanhxay P.

Journal of Material Cycles and Waste Management 22 巻 ( 2 ) 頁： 348 - 353 2020年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Material Cycles and Waste Management

Tungsten carbide-cobalt alloys (WC–Cos), which are used for cutting tools, are mainly composed of tungsten carbide and cobalt with minor elements including chromium, tantalum, nickel. Recycling WC–Cos requires a large amount of energy and chemicals for leaching tungsten. We previously showed that tungsten in WC–COs can be leached by potentiostatic electrolysis at − 0.7 V in molten sodium hydroxide (NaOH) at 723 K; tungsten constituted 99.7 mass% of the leached component in the molten salt. In this study, we investigated tungsten leaching at a lower temperature by using a eutectic mixture of 51.5 mol% NaOH and 49.5 mol% potassium hydroxide (KOH) as the electrolyte. Tungsten was leached from the alloy at temperatures above 623 K, which was 100 K lower than the previous study. Cobalt dissolved in the molten salt, although it formed a passive layer. Chromium underwent oxidization and dissolved as a hexavalent ion below 623 K. Tantalum dissolved even without electrolysis. Tungsten was leached at 623 K in this system. Highly purifying tungsten could be obtained by dissolving the cooled molten salt in water and bringing it in contact with air to precipitate other metal ions. Therefore, the electrochemical process is expected to be used for separating tungsten from WC–Cos.

DOI： 10.1007/s10163-019-00962-x

Nickel–carbon composite plating using a Watts nickel electroplating bath 査読有り国際共著国際誌

Kamimoto Y., Okura S., Hagio T., Wada T., Tanaka H., Hara H., Deevanhxay P., Ichino R.

SN Applied Sciences 2 巻 ( 2 ) 2020年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SN Applied Sciences

Metal–carbon composite platings have potential applications in various fields. We previously reported the preparation of nickel–nanocarbon composite platings using a Wood’s bath. The maximum carbon content was 1.2 mass%, but the maximum current efficiency of plating was 12%. The present study focuses on improving the current efficiency of the electroplating process used to prepare nickel–carbon black composites in a Watts bath contained carbon black. The microstructure and carbon content in the nickel plating were evaluated. The current efficiency was greater than 90%, but the carbon content of the composite plating layer was approximately 0.6 mass%. The incorporation of carbon black particles into the plating layer was influenced by the adsorption of particles onto the cathode surface, the supply of particles to the surface, and the electrodeposition rate. The carbon content in the plating layer was highest near the cathode surface and decreased with increasing thickness of the plating layer. The grain size of electrodeposits with carbon black was larger than that of deposits without carbon black. The space between grains was increased with increasing grain size. The corrosion resistance was diminished, indicating that the boundary was the originating point of corrosion.

DOI： 10.1007/s42452-020-1991-1

Development of magnesium–iron layered double hydroxide and application to nitrate removal 査読有り国際共著国際誌

Kamimoto Y., Okamoto N., Hagio T., Yong-Jun J., Deevanhxay P., Ichino R.

SN Applied Sciences 1 巻 ( 11 ) 2019年11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）出版者・発行元：SN Applied Sciences

Nitrate is an important ion in agriculture and industry although it is known to cause eutrophication and affect human health. Removal of nitrogen by physicochemical treatment such as sedimentation and membrane separation remains difficult. The selectivity of commercial adsorbents for nitrate is among the lowest for anions, because the selectivity of an adsorbent as an ion exchange resin is based on the valence of the ion. Layered double hydroxide acts as an anion adsorbent, and the target anion adsorbs in the interlayer of cations. In this study, we focused on nitrate adsorption by magnesium-iron layered double hydroxide. The results indicate that the magnesium to iron ratio controlled the interlayer distance. The interlayer distance increased as the magnesium to iron ratio increased. The maximum adsorption capacity for nitrate of 1.80 mmol/g suggests the optimum magnesium to iron ratio is 3. The interlayer distance for a magnesium to iron ratio of 3 is similar in size to that of nitrate. The phosphate inhibition of nitrate adsorption suggests the formation of phosphate compounds on the adsorbent’s surface.

DOI： 10.1007/s42452-019-1240-7

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