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Acetylene black, activated carbon, and Ketjenblack were subjected to microwave heating up to 1000 °C under N2 atmosphere to rapidly convert them into graphene-like materials. Few carbon materials exhibit a favorable increase in the intensity of the G’ band with increasing temperature. Upon electric field heating of acetylene black to 1000 °C, the observed relative intensity ratios of D and G bands (or G’ and G band) were equivalent to those of reduced graphene oxide heated under identical conditions. In addition, microwave irradiation under different conditions, i.e., electric field or magnetic field heating, produced graphene of qualities different from those of the same carbon material conventionally treated at the same temperature. We propose that this difference arises from the different mesoscale temperature gradients. The conversion of inexpensive acetylene black and Ketjenblack into graphene-like materials within 2 min of microwave heating is a major achievement toward low-cost mass synthesis of graphene.

Antimicrobial surfactants contained in mouthrinse have excellent efficacy but are not retained on the tooth surface (are rinsed away) due to their low water resistance and thus do not exhibit sustained antibacterial activity. We have developed a new coating method using graphene oxide (GO) that retains the surfactant on the tooth surface even after rinsing with water, thus providing a sustained antibacterial effect. Ultra-thin films of GO and antimicrobial agent were prepared by (1) applying GO to the substrate surface, drying, and thoroughly rinsing with water to remove excess GO to form an ultrathin film (almost a monolayer, transparent) on the substrate surface, then (2) applying antimicrobial cationic surface active agents (CSAAs) on the GO film to form a composite coating film (GO/CSAA). GO/CSAA formation was verified by scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and ζ-potential and contact angle measurements. GO/CSAA was effective at inhibiting the growth of oral pathogens even after up to 7 days of storage in water, and antibacterial activity was recovered by reapplication of the CSAA. Antibacterial GO/CSAA films were also formed on a tooth substrate. The results suggest that GO/CSAA coatings are effective in preventing oral infections.

Oxygen-containing carbon materials such as graphene oxide have been extensively studied because of their high dispersibility. However, the oxygen-containing functional groups in most carbon materials are not controlled. Uncontrollability of the synthesis is also one of factors that prevent industrialization. Carbon materials derived from phloroglucinol (PG), which show high solubility/dispersibility and controllability of functional groups, have been developed recently by our group. The high performance of carbonized PG originates from the thermally stable backbone structure of the benzene ring with hydroxy groups of PG. However, the degree of carbonization was low. In this study, five heteropoly acids (HPAs), which are thermally stable homogeneous strong acid catalysts, were used to promote carbonization of PG without losing the controllability of functional groups and the dispersibility. HPAs promoted etherification of hydroxy groups followed by C=C coupling reactions (furan cyclization) at 523 K. Furthermore, it was confirmed that particularly furan structures, which contribute to solubility/dispersibility in solvents, and thermal stability in air, could be maintained at 673 K as suggested by spectroscopies and thermogravimetric-differential thermal analysis. Among five HPAs, phosphotungstic acid worked as the excellent catalyst to promote carbonization of PG containing furan structures, exhibiting high solubility/dispersibility and high thermal stability in air.

Pentagons in carbon materials have attracted attentions because of the potential high chemical reactivity, band gap control, and electrochemical activity. However, it is challenging to prepare a carbon film with high pentagon density because of the curvature and the high reactivity caused by the presence of pentagons, and it is also challenging to estimate the percentage of pentagons in carbon materials because of the limitation of current analytical techniques. In this work, the percentage of pentagons in carbon materials was experimentally estimated for the first time using experimental and calculated C1s X-ray photoelectron spectroscopy and elemental analysis. Carbon films with 7% of pentagons (40% of pentagons compared to the raw material) with electrical resistivity of 1.1 × 104 Ω meter were prepared by heat treatment of corannulene at 873 K. On the other hand, fluoranthene and fullerene remained as non-film solid and powder without forming films at 873 K. Experimental and calculated Raman and IR spectra revealed the peaks of different types of pentagons. Decrement of pentagons in corannulene and fluoranthene heated at high temperatures can be explained mainly by the scission of C=C bond in pentagons, as suggested by the results of reactive molecular dynamics simulation (ReaxFF).

Oxygen-containing carbon materials such as graphene oxide have been studied intensively for a decade because of the high oxygen content, which is beneficial to disperse carbon materials in solutions and to support either metals or metal oxides on carbon materials. However, various oxygen-containing functional groups exist on carbon materials and controlling the structures is almost impossible. In this work, phloroglucinol (PG), which has a symmetrical structure with three hydroxyl groups relative to six aromatic carbon atoms, was found to be the best precursor among PG, cyanuric acid, trimesic acid, and melamine because of the high yield (63 wt%) at 573 K even in an open system which is essential for mass production. The materials synthesized from PG also showed the high dispersibility and/or solubility in solvents (N-methyl-2-pyrrolidone and N,N-dimethylformamide) and the low temperature to form carbon materials (573 K), which can be explained from (002) and (10) in X-ray diffraction pattern. X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer, carbon-13 nuclear magnetic resonance with the aid of calculation of both spectra and carbonization mechanisms revealed that the high solubility of carbonized PG originates from the presence of ether and cyclic ether, which were formed from dehydration of hydroxy groups, and also some remained hydroxyl groups in carbonized PG. Oxygen-containing groups in carbonized PG were effective as an antioxidant. In addition, the coating of carbonized PG on silica nanoparticles imparted conductivity and lubricity to silica nanoparticles.

Regular diagnosis of the structural health of infrastructure, such as bridges, is indispensable to ensure safety and reliable operation of the society. Non-destructive tests based on X-ray imaging are powerful tools to inspect the inside of a concrete structure in detail. Establishing a diagnostic method of bridges based on X-ray visualization is required to examine the internal conditions and helps in the rationalization of maintenances. We demonstrated our 950 keV X-band electron linac based X-ray source for on-site actual bridge inspection and visualized the inner structure of a bottom floor slab. For the more precise inspection of the conditions of wires and rods, we applied three-dimensional image reconstruction methods for bridge mock-up samples. Partial angle computed tomography and tomosynthesis gave cross section images of the samples with 1 mm resolution. We are planning to investigate another part of the bridge, with the 950 keV X-ray system in the near future.

Cu-doped Li2O, synthesized by mechanochemical reactions between Li2O and CuO, is demonstrated as a cathode material for lithium-ion batteries. The X-ray diffraction and absorption analyses suggest that in the Cu-doped Li2O, Cu2+ ions are located at 48g sites less symmetrical than 8c sites for Li+ ions, distorting the arrangement of surrounding O2− ions slightly from tetrahedral to square-planar, while the Cu2+ ions are doped in an antifluorite-type Li2O. The Cu-doped Li2O cathode has a charge capacity of 360 mAh g−1 without an irreversible O2 gas evolution reaction and exhibits a reversible capacity of 300 mAh g−1. Cu K-edge XANES spectroscopy and quantitative analysis of peroxide species reveal that redox of copper ions, formation/neutralization of O 2p electron holes, and generation/annihilation of peroxide species take place during charge/discharge.

Fe-doped Li2O (FDL) is synthesized mechanochemically and is demonstrated as a new Co-free cathode material for use in sealed Li2O2 batteries, which have been proposed as high energy density batteries. Fe3+ ions are substitutionally doped into the Li sites in an antifluorite-type Li2O structure to create FDL. The FDL consists of (Li0.82Fe0.06)2O (d-FDL) and high-temperature form of Li5FeO4 (o-FDL), in which Fe3+ ions disorderly and orderly arranged, respectively. According to the Mossbauer spectra and quantitative peroxide species analysis, the FDL cathode operates principally based on the redox reaction between O22− and O2−. X-ray diffraction study reveals that the reversible formation of O22− proceeds mainly in the d-FDL. An irreversible side reaction involving the evolution of oxygen gas occurs when the cathode is charged to more than 250 mAh g−1. The FDL (Fe/(Li + Fe) = 10 at%) cathode exhibits a reversible capacity of 200 mAh g−1 over 200 cycles at a current density of 22.5 mA g−1.

We recently proposed a new battery system based on the redox of lithium peroxide (Li 2 O 2 )/lithium oxide (Li 2 O) at the cathode (lithium-peroxide battery system). In this system, the use of Li 2 O with cobalt ions partially substituted for lithium ions (Co-doped Li 2 O) is key to its realization. In this study, to further improve the cell performance, we prepare various Co-doped Li 2 O samples by a mechanochemical process using different cobalt source materials (e.g., LiCoO 2 , Co 3 O 4 , and CoO) and comparatively investigate them. Amongst the investigated cathode materials, the Co-doped Li 2 O sample prepared using LiCoO 2 with a Co/(Co + Li) ratio of 0.09 exhibits the best performance. Monitoring of the pressure in the cell reveals that this Co-doped Li 2 O cathode can be charged to 270 mAh g −1 without O 2 evolution involving its decomposition. Charge and discharge at 270 mAh g −1 is repeated more than 50 times. In addition, the rate-capability tests reveals that the redox reaction between peroxide and oxide ions is fast and that the cathode can be discharged at a high current density of 1000 mA g −1 .

Soft X-ray absorption spectroscopic studies are carried out to clarify the charge/discharge reaction mechanism of Co-doped Li 2 O (CDL, Co/Li = 0.1 molar ratio) as a cathode material for a new rechargeable lithium-peroxide battery. Upon charging CDL in an aprotic electrolyte, a drastic change can be seen in the O K-edge spectra, with a new, strong peak assignable to σ*(O–O) of peroxide at photon energy of 531.0 eV. This peak is reduced during subsequent discharging, causing the spectrum to essentially return to that of pristine CDL recorded in total fluorescence yield mode. The Co L 2,3 -edge spectra do not show a remarkable change during charging, with the exception of the disappearance of a Co 2+ shoulder peak. The spectrum of charged CDL is in reasonable agreement with the calculated spectrum, assuming that the fraction of Co 3+ – L (where L indicates a hole state in the oxygen 2 p band) is dominant in the electronic configuration of the ground state. This suggests that, to a certain extent, a redox reaction involving a ligand hole state (Co 3+ – L ) participates in generation of the capacity.

We propose a new sealed battery operating on a redox reaction between an oxide (O(2-)) and a peroxide (O2(2-)) with its theoretical specific energy of 2570 Wh kg(-1) (897 mAh g(-1), 2.87 V) and demonstrate that a Co-doped Li2O cathode exhibits a reversible capacity over 190 mAh g(-1), a high rate capability, and a good cyclability with a superconcentrated lithium bis(fluorosulfonyl)amide electrolyte in acetonitrile. The reversible capacity is largely dominated by the O(2-)/O2(2-) redox reaction between oxide and peroxide with some contribution of the Co(2+)/Co(3+) redox reaction.

1. Introduction Recently, cathode materials using redox of oxide anion draw increasing attention for development of rechargeable batteries with high energy density. We have proposed a new rechargeable battery system using a redox between oxide and peroxide ions in a cathode material.1 The theoretical energy density is 2570 Wh/kg (voltage: 2.87 V, specific capacity: 897 mAh/g), assuming that the redox between Li2O and Li2O2. We have demonstrated that the battery system with Co-doped Li2O (CDL) as a cathode material exhibits a reversible capacity of 270 mAh/g operating on the redox of oxide and peroxide ions.1,2 But this obtained capacity is far less than the theoretical one. Therefore, there must be room for enhancing the specific capacity. For further improving the battery system, deeper knowledge and better understanding of charge/discharge mechanism of the CDL are required. X-ray absorption spectroscopy (XAS) is an effective method to investigate electronic states and coordination structures of elements of interest in a sample.1,3 In this study, we investigated the states of cobalt and oxygen in the CDL during charge and discharge by using both hard and soft XAS. 2. Experimental The CDL (Co/(Li+Co) = 0.09) was prepared from Li2O and LiCoO2 by using a planetary ball-mill.2 The CDL was mixed with acetylene black and polytetrafluoroethylene at a weight ratio of 75:20:5 or 85:10:5 to serve as cathodes. The cathode material pressed onto aluminum mesh, lithium metal as an anode, an electrolyte solution of 1 M LiBF4 dissolved in a mixture (1:1 by volume) of ethylene carbonate (EC) and diethyl carbonate (DEC), and a glass-fiber filter as a separator were assembled in a 2032 coin-type cell. All these procedures were operated in an argon-filled glove box. The cell was charged to 270 mAh/g and then discharged to 270 mAh/g at a current density of 4.5 mA/g at 298 K. The cathodes charged or discharged to various depths were removed from the cell, washed with EC-DEC once and with DEC twice, and dried under vacuum for XAS measurements. The hard XAS measurements at Co K-edge were carried out at the beam line BL9A of the Photon Factory in High Energy Accelerator Research Organization in a transmittance mode. The samples were packed in laminated aluminum foil bags. The soft XAS measurements at O K-edge were carried out at the beam line BL2 of Ritsumeikan University SR Center in both total electron yield (TEY) and partial fluorescence yield (PFY) modes. The samples were transferred to high-vacuum chamber of BL2 by using a transfer vessel filled with argon gas. 3. Results and discussion XAS spectra at Co K-edge were measured for the CDL charged and discharged in increments of 45 mAh/g. In the charge process, the absorption edge shifts to higher energy by 1.0 eV from 0 to 135 mAh/g and remains in almost the same position from 135 to 270 mAh/g. In the discharge process after charging to 270 mAh/g, the absorption edge gradually shifts to lower energy by 1.0 eV from 0 to 225 mAh/g and sharply shifts to lower energy by 1.3 eV from 225 to 270 mAh/g. XAS spectra at O K-edge were measured for the CDL charged and discharged in increments of 90 mAh/g. In the charge process from 0 to 90 mAh/g, a broad peak at 528 eV, which is attributed to electron transition from O 1s to Co 3d-O 2p hybridized states, increases in its intensity. In the charge process from 90 to 270 mAh/g, a new peak appears at 530 eV. This peak is attributed to peroxide in CDL since Li2O2 shows a peak attributed to electron transition from O 1s to σ*(O-O) at the same energy. In the discharge process, the peak at 530 eV weakens and disappears from 0 to 180 mAh/g and the broad peak at 528 eV decreases in its intensity from 180 to 270 mAh/g. These results suggest that the Co 3d-O 2p hybridized states contribute to charge transfer in the earlier charge period and the later discharge period. The formation and decomposition of peroxide species in the later charge period and the earlier discharge period, respectively, are spectroscopically traced, which are consistent with our previous results of chemical peroxide analysis.1 Acknowledgements This work was supported by JSPS Grant-in-Aid for Young Scientist (B) Grant Number 15K18326 and JSPS Grant-in-Aid for Scientific Researches (B) Grant Number 26289371. The XAS measurements were carried out under the approvals of the Photon Factory Program Advisory Committee (Proposal No. 2015G698). References 1. S. Okuoka et al., Sci. Rep., 4, 5684 (2014). 2. H. Kobayashi et al., J. Power Sources, 306, 567 (2016). 3. Y. Ogasawara et al., J. Power Sources, 287, 220 (2015). Figure 1

Introduction We recently proposed a novel lithium-ion battery system based on a redox reaction between oxide ions and peroxide ions at a cathode, and demonstrated the system with a Co-doped Li2O cathode, in which Co ions were located at the same sites as Li+ ions.1 In these earlier studies, the Co-doped Li2O exhibited a specific capacity of 270 mAh g−1 with 50-cycle durability.2 However, the specific capacity of 270 mAh g−1 was much smaller than the theoretical specific capacity of 897 mAh g–1 on the basis of Li2O2 + 2Li = 2Li2O. In the present study, we aimed at improving the cell performance with the Co-doped Li2O cathode and clarifying the mechanism of reactions during charging/discharging. Experimental The sample was prepared by pulverization of mixture of Li2O and LiCoO2 with a planetary ball mill at 600 rpm for 10 h. The starting materials were set so that the atomic ratio (Co/(Co+Li)) in the mixture was 0.09, which had been optimized in our previous study.2 XRD analysis revealed that the prepared sample contained (Li0.82Co0.058□0.12)2O (Co-doped Li2O) and LiCoO2 at the molar ratio of 95:5, where □ represents a Li+-site vacancy. The sample was mixed with ketjen black and polytetrafluoroethylene at the weight ratio of 75:20:5 and typically 10 mg of the mixtures were pressed onto an Al mesh current collector. Thus fabricated electrode was immersed in vinylene carbonate (VC) for 1 h and dried in vacuum. The VC-treated cathode, Li metal as an anode, an electrolyte, and a glass-fiber filter as a separator were assembled in a 2032 coin-type cell. The electrolyte solution was 1 M LiPF6 dissolved in a mixture (1:1 by volume) of ethylene carbonate (EC) and dimethyl carbonate (DMC), with a 5vol% VC additive. The aforementioned operations were conducted in an Ar-filled glove box. Charge/discharge tests between 1.7 and 3.5 V were carried out at 25 °C in a constant-current mode at the current density of 50 mA g–1. Pressure change in a cell was monitored using a pressure gauge connected to the cell. The lower detection limit of the pressure was 5×102 Pa, which corresponded to 6 mmol per 1 mol of the empirical formula of Co-doped Li2O. Results and discussion Figure 1(a) shows voltage curves of the cathode during charge/discharge and pressure in the cell during charge. The charging voltage increased to 3.2 V at 0–150 mAh g–1, and reached a 3.2 V plateau region at 150–400 mAh g–1. Pressure started increasing at around 320 mAh g–1, indicating that an irreversible O2 evolution reaction occurred. During the following discharge, the voltage curve contained a plateau region at 2.7–3.1 V and a slope region at 1.7–2.7 V, and showed capacity of 410 mAh g–1. This capacity was higher than that of the preceding first charge, during which the irreversible O2 evolution reaction occurred. This is because the capacity by the reduction from Co3+ to Co2+ was greater than the irreversible capacity due to the O2 evolution. The capacity 410 mAh g–1 was much higher than our previous reported value 270 mAh g–1, which is due to the pretreatment with VC. Although the mechanism enhancing the specific capacity by the VC treatment has not been clarified, we confirmed from separately conducted experiments that VC was more effective as a pretreatment agent than an additive into an electrolyte. After the first cycle, the charge/discharge was carried out with the charge depth reset to 410 mAh g–1, which was the capacity of the first discharge. Fig. 1(b) exhibits second charge/discharge profiles and pressure in the cell during second charge. The second charge curve differed from the first one; a slope region at around 2.3 V due to oxidation of Co2+ appeared. No change in pressure was observed in the whole region, indicating that the evolved O2 gas during the second charge was below the detection limit (5×102 Pa). The following discharge curve was similar to that of the first discharge. The coulombic efficiency (= discharge capacity/charge capacity) was 98.8%. The voltage curves for a multi-cycle test are shown in Fig. 1(c). While the charge/discharge curves present little changes in shape, the discharge capacity gradually decreased with cycles to be 400 mAh g–1at 10th cycle. Acknowledgments A part of this work was conducted with the support of JSPS Grant-in-Aid for Scientific Researches (B) Grant Number 26289371 and the support of JSPS Grant-in-Aid for Young Scientists (B) Grant Number 15K18326. References 1. S. Okuoka et al., Sci. Rep., 4, 5684 (2014). 2. H. Kobayashi et al., J. Power Sources, 306, 567 (2016). Figure 1

It is well known that the creep of concrete is influenced by the ambient relative humidity. But there is no sufficient information about the effects of moisture content in concrete specimens at the loading age on the creep behaviour and other mechanical properties. This experimental program was carried out to investigate the effects of moisture content on the strength and creep of concrete under uniaxial and triaxial (i.e. hydrostatic pressure) compressive stress at 30°C. And the dependence of moisture content on the visco-elasticity of concrete was discussed rheologically. The compression creep tests were performed under the following conditions; the moisture contents were 100% (wet), 68, 44, 14, 0 (dry) and -4% (over dry), and the creep stresses applied to the sealed concrete specimens were 100, 200 and 300 (kgf/cm2).The test results showed that the compressive strength, Fc and the elastic strain, ec of concrete decreased with increasing moisture content, φ. It was considered that the strength reduction may be due to the change of surface energy, γ in the hydrated cement gel, and the larger elastic strain at lower moisture content level was brought in as the result of growing of void and crack in concrete during drying procedure. On the other hand, the moisture dependency of creep strain, ec was greatly different from the case of elastic strain: the magnitude of creep strain increased rapidly with increasing moisture from 0% to 40%, and then became nearly constant in the range of 40% over. From these facts, it was considered that the refraction point at 40% moisture in the (φ-ec) curve was brought by the repulsiveforce disjoining pressure which acts among many gel particles.

Since the accelerated electron has by far a higher dose rate than gamma-rays, the electron polymerizing method is more suitable for the efficient fabrication of polymer-impregnated concrete (PIC) with a thin cross section. However, there are few published papers on the manufacturing process of PIC polymerized by electron beam.This experiment was carried out to investigate the effects of density of cement mortar, dose rate of electron beam (4MeV), total exposure dose and other factors which have influences upon the strength of MMA-PIC. The density of mortar, size of cross section of mortar specimens, dose rate of electron, total exposure dose and irradiating time interval were varied respectively as follow; ρ=1.55∼3.13g/cm3 (the kinds of aggregates in cement mortar used are perlite, artificial light weight aggregate, normal river sand and iron sand), t=3.5∼40mm in thickness, 0.55 or 1.10 Mrads/sec, 12.5∼100 Mrads per face, and 15∼60sec/cycle.The test results of mechanical strength of PIC show that the optimum total exposure dose is about 40Mrads at 0.55Mrads/sec rate and 50Mrads at 1.1Mrads/sec in the ordinary mortar. It is also shown that the impregnation depth from the surface of specimen has a linear relation with the density of cement mortar, and that its depth is about 1cm in conventional mortar.

It is well-known that the polymer impregnated concrete (PIC) has many excellent characteristics such as high compressive strength of over 1500kg/cm2, large elongation capacity, negligibly small water permeability and no-shrinkage. And it has also been reported by BNL and USBR that PIC shows good resistance to chemical attack. However, the chemical stability of PIC has been evaluated only form its weight loss, but scarecely from the loss of its mechanical strength.In this paper, the losses in weight and strength of a plain mortar, a mortar (PIC) impregnated with poly-methyl-methacrylate polymerized by thermal-catalyzer with BPO=5%, and a mortar impregnated with polypropylene fiber reinforced polymer were examined in order to obtain their resistance to chemical attack by 10%-HCl, 10%-MgSO4, 10%-CH3COOH and pure C6H6.The results showed that the weight loss of PIC (18.6%) was less than that of the plain mortar (24%), when attacked by 10%-HCl for 28 days. The losses in compressive strength of PIC and plain mortar after attacked by HCl were 67% and 97%, respectively; and after attacked by CH3COOH the losses were 26% and 57%, respectively. So, it can be said from the viewpoint of compressive strength that the chemical resistance of PIC is 23 times that of the plain mortar against HCl and 3.6 times against CH3COOH.

Although the polymer impregnated concrete (PIC) has such excellent characteristics as high strength, small water permeability, high corrosion resistance and no shrinkage, it has such weak points as low impact strength, no plastic range in strain and low toughness.In the present paper, the mechanical properties of fiber reinforced polymer impregnated concrete have been investigated by using several fibers, made of glass, polypropylene and metal, and MMA-and SM-monomers. The main results obtained are as follows:Among the five kinds of fiber examined, piano wire with 0.2mm diameter and 35mm length was most effective. The strengths of FPIC reinforced by the piano wire were 2003kg/cm2 for compressive, 536kg/cm2 for flexural, 195kg/cm2 for tensile, and 186kg/cm2 for Charpy's impact strength, whereas those of plain mortar cured in water were 593, 73, 36 and 8.7kg/cm2, respectively. And from the fact that the tensile maximum strain at the ultimate strength obtained in repeated bending test for PW-PIC beam 2500×10-6, it is deduced that FPIC-material has large toughness and has far more useful properties than PIC.