Vapor Grown Carbon Fiber Research Articles

Preparation Procedures of Pt-Decorated SnO2 Electrocatalysts on Conductive Fillers

For polymer electrolyte fuel cells (PEFCs), the electrocatalysts with Pt nano-particles homogeneously dispersed on carbon black (Pt/C) are widely used. However, during the fuel cell start-stop cycles, the potential of the cathode can reach up to ca. 1.5V, resulting in a severe carbon corrosion. Tin oxide (SnO2) has been studied as an alternative support material because of its thermochemical stability. Takasaki et al. [1] have demonstrated negligible degradation within 60,000 cycles in a half-cell test, indicating that Pt/SnO2 electrocatalyst can exhibit an excellent voltage cycle durability. However, relatively low electrical conductivity in such semiconducting oxides often leads to poor cell performance. In the previous PEFC Symposium in Cancun, we reported higher activity of Pt/SnO2 electrocatalysts on conductive fillers acting as the backbones of the electrocatalysts [2]. We selected vapor grown carbon fibers (VGCF) and acetylene black (AB) as possible conductive fillers, and Pt/SnO2/VGCF and Pt/SnO2/AB were synthesized. Their electrochemical surface area (ECSA) was about three times as large as that of Pt/SnO2. However, they are slightly inferior to the ECSA of Pt/C. Here, we aim to improve the electrochemical activity of Pt/SnO2electrocatalysts on conductive fillers approaching that of the state-of-the-art Pt/C electrocatalyst. First, we have reexamined the procedure for the preparation of SnO2. Previously, SnO2/VGCF and SnO2/AB were synthesized via the ammonia co-precipitation. In this process, due to heat treatment required at a high temperature (e.g. 600oC), the particles of SnO2 were agglomerated. We thus introduced a homogeneous precipitation procedure using microwaves which requires no heat treatment at a high temperature. Consequently, the BET specific surface area of SnO2becomes one order of magnitude larger. Second, we have adjusted the loading of SnO2 for the conductive fillers. The BET specific surface area of SnO2/VGCF becomes larger with increasing SnO2 loading. However, their electrochemical activity decreased for too high SnO2 loading, due to its lower electrical conductivity. In addition, the catalytic activity was improved by heat treatment to 200 or 400oC. The details on the catalytic activity increase by optimizing SnO2loading and heat treatment temperature will be presented at the meeting. [1] F. Takasaki et al., J. Electrochem. Soc., 158(10) B1270 (2011). [2] D. Horiguchi et al., ECS Trans., 64(3) 215 (2014). Figure 1

Effect of Pore Volume of Hydrophilic Microporous Layer (MPL) on PEFC Performance

The effect of the microporous layer (MPL) on membrane electrode assemblies (MEAs) has been investigated. The performance of an MEA employing an MPL with a larger pore volume was better under both 100%RH and 30%RH conditions. We reported that the MEA using a hydrophilic MPL showed much better performance in a wide range of pressure and humidity conditions than that using a hydrophobic MPL (1, 2). The hydrophilic MPL consists of vapor-grown carbon fiber with a fiber diameter of 150 nm and ionomer. We applied our technique of preparing a carbon fiber dispersion to the fabrication of MPLs using carbon particles and carbon fibers with various fiber diameters. Properties of carbon materials and MPLs are shown in Table 1. The pore size distribution (Fig. 1) was measured using mercury intrusion porosimetry (Auto Pore IV 9500, Shimadzu Co.). Figure 2 shows the surface SEM images of the MPLs: The MPL made of carbon black (Vulcan XC) has the smallest pore diameter (0.068 μm) and that made of carbon fiber (VGCF-H) has the largest pore diameter (0.77 μm). Although carbon fiber CF-X has the largest fiber diameter of 250 nm, the MPL made of it has a smaller pore volume. This is probably because fibers of CF-X are straight and longer than other carbon fibers, tending not to become tangled and form larger pores. MEAs having an MPL made of four different carbon materials (Vulcan, 24PS, VGCF-H, and CF-X) were prepared, and polarization curves were measured under the conditions of 80 ºC, 100%RH & 30%RH. The estimated mass transfer loss based on the polarization curves (80 ºC, 100%RH) for the four MEAs are plotted against the pore volume of MPL in Fig. 3. The larger the pore volume of MPL, the smaller the mass transfer loss becomes. The MEA employing a hydrophilic MPL with a larger pore volume also showed higher cell voltage under the dry condition of 80 ºC, 30%RH. It was found that the pores of the hydrophilic MPL play a crucial role in achieving excellent MEA performance, such as mitigating cathode flooding under the wet condition and high cell voltage under the dry condition by preventing the membrane from drying.

Characteristics of Fe2O3/exfoliated vapor-grown carbon fiber composite as anode material for lithium-ion batteries

The effect of exfoliation of vapor-grown carbon fiber (VGCF) on the electrochemical properties as an anode of lithium-ion batteries was thoroughly investigated by diverse characterization tools. The exfoliation by the ball milling followed by the acid and heat treatments changed several morphological features such as decreased length, wider interlayer spacing, and even exfoliation of the layer. Moreover, numerous defects including functional groups were observed when the VGCF was exfoliated, increasing the deposition of Fe2O3 on its surface. Owing to these advantages, the exfoliated-VGCF exhibited significantly enhanced C-rate capability with high reversible capacity even though its initial irreversible capacity increased compared to the pristine VGCF. In particular, the Fe2O3/exfoliated-VGCF composite anodes have a good cycle stability with a high capacity of 936 mA h g−1 after 50th discharge at a C-rate of 100 mA g−1.

Facile fabrication of superhydrophobic conductive graphite nanoplatelet/vapor-grown carbon fiber/polypropylene composite coatings

Abstract The fabrication of superhydrophobic surfaces with mechanical durability is challenging because the surface microstructure is easily damaged. Herein, we report superhydrophobic conductive graphite nanoplatelet (GNP)/vapor-grown carbon fiber (VGCF)/polypropylene (PP) composite coatings with mechanical durability by a hot-pressing method. The as-prepared GNP/VGCF/PP composite coatings showed water contact angle (WCA) above 150° and sliding angle (SA) less than 5°. The superhydrophobicity was improved with the increase of VGCF content in the hybrid GNP and VGCF fillers. The more VGCFs added in the GNP/VGCF/PP composite coating, the higher porosity on the surface was formed. Compared to the GNP/PP and VGCF/PP composite coatings, the GNP and VGCF hybrid fillers exhibited more remarkable synergistic effect on the electrical conductivity of the GNP/VGCF/PP composite coatings. The GNP/VGCF/PP composite coating with GNP:VGCF = 2:1 possessed a sheet resistance of 1 Ω/sq. After abrasion test, the rough microstructure of the GNP/VGCF/PP (2:1) composite coating was mostly restored and the composite coating retained superhydrophobicity, but not for the VGCF/PP composite coating. When the superhydrophobic surface is mechanically damaged with a loss of superhydrophobicity, it can be easily repaired by a simple way with adhesive tapes. Moreover, the oil-fouled composite surface can regenerate superhydrophobicity by wetting the surface with alcohol and subsequently burning off alcohol.

Enhanced Electrochemical Characteristics of the Pani-Coated Sulfur Cathode

The dissolution of polysulfides from the cathode remains a key roadblock in the advancement of Li-S batteries. To prevent polysulfide dissolution and improve the performance of Li-S battery, PANi-coated sulfur cathode is prepared using 2L reaction vessel. Using the different sulfur ratio, the performance test is conducted, which results that 33 wt% sulfur PANi composite shows best performance. The PANi-coated sulfur composite cathode was composed of 70 wt% of the PANi-coated sulfur composite, 20 wt% of vapor grown carbon fiber, and 10 wt% of binder (kynar 761). The bare sulfur cathode also had a similar composition (70 wt% of sulfur, 20 wt% of vapor-grown carbon fiber, and 10 wt% of binder (kynar 761)). The sulfur loading of the electrodes was about 4.5 mg cm-2. The electrode slurry was coated on an aluminum sheet (15 µm).

Carbon black and vapor grown carbon fibers binary conductive additive for the Li1.18Co0.15Ni0.15Mn0.52O2 electrodes for Li-ion batteries

Carbon black (CB) and vapor-grown carbon fibers (VGCFs) are used as conductive additives for the Li1.18Co0.15Ni0.15Mn0.52O2 electrodes for Li-ion batteries. The fibrous VGCFs can bridge the isolated Li1.18Ni0.15Co0.15Mn0.52O2 regions, thus construct an effective conductive network for electron transport. In addition, incorporation of CB and VGCFs can improve the electrochemical kinetics of the cathode material by retarding the harmful side reactions, promoting the charge transfer reactions and increasing the apparent lithium diffusion coefficient. In all electrodes under investigation, the one prepared with 3 wt.% of VGCFs and 12 wt.% of CB shows the largest discharge capacity of 252 mAh g−1 at the 0.2C rate with excellent capacity retention and rate capability.

A comparative investigation of carbon black (Super-P) and vapor-grown carbon fibers (VGCFs) as conductive additives for lithium-ion battery cathodes

The synergistic effect of different types of conductive additives, vapor-grown carbon fibers (VGCF) and carbon black (Super-P) on the cathode performance of lithium-ion batteries was investigated.

G0400506 炭素繊維含有アルミニウム基複合材料の機械的性質と微視観察

Recently, aluminium (Al) based composites containing each carbon fibers (CF), such as carbon nanotubes (CNT), and vapor-growth carbon fibers (VGCF), are actively developed. These fibers have high thermal conductivities and high strengths. And then Al/VGCF composites fabricated using spark plasma sintering are known to have a high thermal conductivity. The composites are anticipated using for the application of heat exchangers. In this paper, an Al/CF composite are fabricated using sintering process. The relationship between microstructures and mechanical properties are considered using the sintering composites. First, an optimum sintering conditions of matrix in Al and Aluminum silicon eutectic alloy (Al-12Si) are considered, by measurement of porosity ratio, Vickers hardness test, and microscopic observation. And then, a relationship between microstructure of the composite and the hardness are considered. According to the experimental results, the composite with Al-12Si has lower porosity ratio than the composite without Al-12Si. The Vickers hardness correlates highly with the porosity ratio.

Influence of addition of vapor grown carbon fibers on mechanical, thermal and biodegradation properties of lignin nanoparticle filled bio-poly(trimethylene terephthalate) hybrid nanocomposites

Bio-poly(trimethylene terephthalate) (bio-PTT) hybrid nanocomposites constituting 1.5 wt% of lignin nanoparticles (LNP) and variable wt% of vapor-grown carbon fibers (VGCF) were prepared using melt extrusion followed by a microinjection molding technique.

Effect of hybrid conductive additives on all-solid-state lithium batteries using Li2S–P2S5 glass-ceramics

In order to enhance the electrochemical performance of all-solid-state composite cathodes, a hybrid of conductive additives consisting of Vapor Grown Carbon Fiber (VGCF), which had a high aspect ratio, and Super P carbon with a high surface area, were employed in all-solid-state composite cathodes. The effect of these additives on the electrochemical properties and microstructure was investigated. Microstructures that had valid electron conducting networks consisting of short-range conducting paths crossing the surfaces of individual LiCoO2 particles and long-range conducting paths linking neighboring LiCoO2 particles were obtained by blending of fibrous VGCF with nano-sized spherical Super P carbon particles. As a result, the all-solid-state composite cathodes using hybrid conductive additives showed a higher electronic conductivity and lower charge-transfer resistance compared with those using single conductive additives, which resulted in the highest discharge capacity of 68mAhg−1 at 1C and 38mAhg−1 at 2C when using the all-solid-state composite cathode with 2wt% of VGCF and 1wt% of Super P carbon. This indicated that the use of a hybrid conductive additive was a suitable and effective method to enhance the reversible capacity of the all-solid-state composite cathode at high current densities.

Investigation on mode-II interface fracture toughness of CFRP/Al laminates toughened by VGCF interleaves

Mode-II interlaminar mechanical properties of CFRP/Al(aluminum) laminates were improved by acid treatment to an Al plate and adding vapor-grown carbon fiber (VGCF) between the Al plate and a CFRP layer. The influence of VGCF addition on the Mode-II interlaminar mechanical properties was explored by end-notched flexure tests. The experimental results demonstrated that the critical load and Mode-II fracture toughness of the specimen with acid treatment and 10 g/m2 addition of VGCF increase by 73.66 and 175.76 %, respectively, compared to those of the specimen with acid treatment only. The improvement mechanisms were investigated by the observation of crack propagation path and fracture surface under laser scanning and scanning electron microscopies. Moreover, finite element analyses were undertaken based on the cohesive zone model to verify the experimental fracture toughness and to predict the interfacial shear strength between the Al plate and the CFRP layer.

Influence of viscoelasticity on friction coefficient of abrasive wear for filler-dispersed polyamide 6

The friction and wear properties of polyamide 6 dispersed with titanium carbide particles, aluminum borate whiskers and vapor-grown carbon fibers have been investigated in relation with the filler type, the filler content, the roughness of abrasive paper and the sliding velocity. The results have been analyzed based on an abrasive wear model using an expression μ=(gσs)/(kH) where μ is the friction coefficient, g is the shape factor of the abrasive particle, σs is the stress required for sliding the abrasive particle, k=1.08 and H is the microhardness. The PA6 and the composite films showed abrasive wear except for the ABW/PA6 and TCP/PA6 films worn with a fine abrasive paper which showed adhesive wear. For abrasive wear, the decrease in the roughness of abrasive paper and the increase in the sliding velocity both increased the storage modulus due to viscoelasticity. This led to the decrease in the penetration depth and g. As a result, the friction coefficient of the PA6 and the composite films decreased. On the other hand, the filler type and the filler content influenced the friction coefficient through the changes in σs and H.

Hydrogen-Bonding Assembly of Rigid-Rod Poly(p-sulfophenylene terephthalamide) and Flexible-Chain Poly(vinyl alcohol) for Transparent, Strong, and Tough Molecular Composites

Molecular composites comprising poly(p-sulfophenylene terephthalamide) (sPPTA), a sulfonated polyaramid rigid-rod polyelectrolyte, and flexible-chain poly(vinyl alcohol) (PVA) were prepared by a green and easy-to-scale-up water casting method. Influence of sPPTA on the microstructure and properties of the molecular composites was systematically investigated. Fourier transform infrared spectroscopy confirms the existence of hydrogen bonding between sPPTA and PVA. Wide-angle X-ray diffraction patterns do not show the characteristic of neat sPPTA crystalline aggregates in the composites even when the sPPTA content is as high as 33 wt %, suggesting that the strong interaction between sPPTA and PVA prevents the self-aggregation of sPPTA and leads to the formation of PVA/sPPTA complexes inside the composites. Transmission electron microscopy shows that sPPTA has good compatibility with PVA, and nanoscale fibril-like supramolecular assemblies dispersing uniformly in the composites become observable with the increase of sPPTA content. Moreover, the PVA/sPPTA complexes have a strong effect on the melt point, crystallinity, mechanical properties, and thermal stability of PVA. The PVA/sPPTA composites exhibit both high strength and high ductility. When the content of sPPTA is 5 wt %, the PVA/sPPTA composite exhibits the best mechanical properties, with a tensile strength of 169 ± 13 MPa, which is 54% higher than that of neat PVA (110 ± 10 MPa). Surprisingly, the reinforcement factor is even superior to that of multiwalled carbon nanotubes, vapor grown carbon fibers, and nanodiamonds previously reported for the reinforcement of PVA nanocomposites. Moreover, the PVA/sPPTA molecular composites have a relatively low modulus but a much larger elongation at break than prefabricated nanocomposites, showing good ductility. The strong and tough PVA/sPPTA molecular composites can be potentially used as high performance membranes or fibers in the future.

Nanoparticulate Mn3O4/VGCF composite conversion-anode material with extraordinarily high capacity and excellent rate capability for lithium ion batteries.

In this work, highly conductive vapor grown carbon fiber (VGCF) was applied as an electrically conductive agent for facile synthesis of a nanoparticulate Mn3O4/VGCF composite material. This material exhibits super high specific capacity and excellent rate capability as a conversion-anode for lithium ion batteries. Rate performance test result demonstrates that at the discharge/charge current density of 0.2 A g(-1) a reversible capacity of ca. 950 mAh g(-1) is delivered, and when the current rate is increased to a high current density of 5 A g(-1), a reversible capacity of ca. 390 mAh g(-1) is retained. Cyclic performance examination conducted at the current density of 0.5 A g(-1) reveals that in the initial 20 cycles the reversible capacity decreases gradually from 855 to 747 mAh g(-1). However, since then, it increases gradually with cycle number increasing, and after 200 cycles an extraordinarily high reversible capacity of 1391 mAh g(-1) is achieved.

Silicon anode for rechargeable aqueous lithium–air batteries

A novel aqueous lithium–air rechargeable cell with the configuration of Si/1 M LiClO4 in ethylene carbonate–diethylene carbonate/Li1+x+yAlx(Ti,Ge)2−xP3−ySiyO12/5 M LiCl–1 M LiOH aqueous solution/carbon black, air is proposed. A silicon anode composed of mechanically milled silicon power with an average particle size of ca. 0.5 μm, vapor grown carbon fiber and a polyimide binder was examined. The open-circuit voltage at the charged state was 2.9 V at 25 °C. The discharge capacity of 700 mAh g-silicon−1 was retained for 40 cycles at 0.3 mA cm−2 with cut-off voltages of 3.5 and 1.5 V. Significant capacity fade was observed at deep charge and discharge cycling at 2000 mAh g-silicon−1.

Thermal conductivity of polypropylene composites with hybrid fillers of boron nitride and vapor‐grown carbon fiber

High thermal conductivity fillers of boron nitride (BN) and vapor‐grown carbon fiber (VGCF) were used alone or incorporate to prepare polypropylene (PP) composites. The effects of filler content, particle size and shape, and single vs. hybrid BN/VGCF fillers were investigated with respect to the thermal conductivity of the PP composites. The thermal conductivity of PP/BN composites depended upon the content and particle size of the BN. Increased content and length of VGCF had the effect of increasing the thermal conductivity of the PP composites. Hybrid fillers were created with a mixture of medium‐sized BN and long‐length VGCF; hybrid BN/VGCF fillers enhanced the thermal conductivity of PP composites with a lower total content compared with PP composites containing only medium‐sized BN particles. POLYM. COMPOS., 37:936–942, 2016. © 2014 Society of Plastics Engineers

Experimental and numerical study on the improvement of interlaminar mechanical properties of Al/CFRP laminates

Improvement of interlaminar mechanical properties in Al/CFRP laminates, fabricated by carbon fiber reinforced plastic (CFRP) prepregs combined with Al alloy sheets, was studied experimentally and numerically. Three toughening methods including acid etching and mechanical patterning for surface treatment of Al alloy sheet, as well as addition of nanofiller (i.e., vapor grown carbon fiber (VGCF)) to the interface of CFRP and Al sheet, were investigated. Experimental results of double cantilever beam tests show the improvement on the interlaminar mechanical properties of Mode-I fracture in terms of much higher critical load PC and fracture toughness GIC. The highest GIC was obtained in the specimens with the combination of acid etching on Al sheet and 10g/m2 VGCF addition, which was 41 and 6.5 times higher than those of the pristine samples without any treatment and the samples with only acid etching, respectively. Although further mechanical patterning had a positive effect for the case without VGCF addition, the minor effect was observed for the case of VGCF addition because of difficult dispersion of VGCF. Crack propagation and fracture surface were also observed to interpret the improvement mechanism. Moreover, by using the above experimental GIC, finite element analyses were carried out based on cohesive zone model to numerically simulate delamination propagation. The numerically predicted interlaminar tensile strength of Al/CFRP laminates also shows great improvement of interlaminar mechanical properties using the above toughening methods.

In Situ Soft X-ray Visualization of Liquid Water Distribution in a PEMFC with VGCF-Modified MPL

In proton exchange membrane fuel cells (PEMFCs), appropriate water management is critical to achieve high power density operation with increased robustness. For this purpose, soft X-ray radiography has been used in this study because it has been proved to be a powerful incitement for observing liquid water in PEMFCs. In this study, we focused our attention on micro porous layers (MPLs) with vapor growth carbon fiber (VGCF) impregnated in the MEA. In the experiment, we fabricated VGCF MPL coated on gas diffusion substrate (SIGRACET® 24BA). We also used commercial gas diffusion layer (SIGRACET® 24BC) for comparison. In situ visualization of liquid water distribution in both MEAs by soft X-ray radiography clearly shows their difference. The water tends to accumulate both at GDS and MPL for 24BC; the water tends to accumulate at GDS for VGCF.

Surface modification of carbonaceous materials and their use in polymer electrolyte fuel cells and hydrogen-air secondary batteries

Surface modification techniques for carbonaceous materials such as composites, Ketjen black, and vapor grown carbon fibers (VGCFs) are introduced and their use in polymer electrolyte fuel cells (PEFCs) and hydrogen-air secondary batteries are reviewed. A graphite powder/resin composite used as a bipolar plate of PEFCs is corroded with the evolution of CO 2 over 1.3 V in a dilute HClO 4 solution at 80 °C. A tin oxide coating is found to be effective in preventing corrosion. A similar effect of a tin oxide coating is also found for Ketjen black as the electrode catalyst support of PEFCs. Furthermore, after loading Pt as the catalyst it is found that the tin oxide coating of Ketjen black gives better catalytic activity. O -Methylated Ketjen black is prepared and its performance as the catalyst support is also discussed. VGCFs decorated with LaMnO 3 are also prepared and have promise as the electrode material for a hydrogen-air secondary battery. [TANSO 2014 (No. 263) 114–22.]

In Situ Soft X-ray Visualization of Liquid Water Distribution in a PEMFC with VGCF-Modified MPL

In proton exchange membrane fuel cells (PEMFCs), appropriate water management is critical to achieve high power density operation with increased robustness. Proton exchange membranes (PEMs) require sufficient hydration to fulfill its function as proton conductor, while flooding at the cathode side can hamper the transport of reactant, resulting in deterioration of cell operation. Liquid water transport and accumulation should be affected by materials impregnated in membrane electrode assemblies (MEAs) and this causes variation of cell performance. This motivated us to investigate effects of impregnated materials in MEAs on liquid water accumulation behaviors and resultant cell performance. For this purpose, soft X-ray radiography has been proof it is a powerful incitement for observing liquid water in PEMFCs because of the high spatial and temporal resolution. [1-5]In this study, we focused our attention on micro porous layers (MPLs) with vapor growth carbon fiber (VGCF, Unitetek international co. LTD, Taiwan) impregnated in MEA, because VGCF-modified MPLs have been shown for better cell performance especially in high current density operation, suggesting an improvement on liquid water transport [6]. We first examined polarization curves of two types of MEAs with or without VGCF in MPL. In Fig.1, we observed better cell performance with a MEA with VGCF-modified MPL than those with a conventional MEA without VGCF. In the experiment, we fabricated VGCF MPL coated on gas diffusion substrate (SIGRACET® 24BA). We also used commercial gas diffusion layer (SIGRACET® 24BC) for comparison. In both MEAs, we fabricated catalyst coated membranes (CCMs) by decal transfer method. Nafion® 212 had been selected as the membrane and the same batch of catalyst layer with 0.27mgPt cm-2 loading had been used. The hydrogen and air were fed at 200mL min-1 and 500mL min-1 for a 5cm-2 (23 mm x 23 mm) active area normal cell, respectively. The channel width and depth were 1.0 and 1.0 mm. The rib-to-channel ratio was 1 for normal cell. For a X-ray cell (0.03cm-2, 1 mm x 3 mm), hydrogen and air were both fed at 15mL min-1. The channel width and depth were 0.5 and 0.5 mm. The rib-to-channel ratio was 1 for X-ray cell. Cell operating temperature was set at 80°C and relative humidity of the reactants was kept at 92%. In situ visualization of liquid water distribution in both MEAs by soft X-ray radiography clearly shows their difference as shown in Fig.2. Form the original image Fig.2 (a) and (b), we can found VGCF sample (Fig.2(b)) was difficult to recognize the MPL. The one of the reason is the MPL infiltrate into gas diffusion substrate and another reason is the VGCF MPL maybe has high porosity thus it didn’t absorb much soft X-ray cause to similar intensity of GDL and VGCF-MPL. In both cases (Fig.2(c) and (d)), liquid water was observed under the rib, however, for VGCF-modified MPL at 0.7A cm-2 (Fig.2(d)), less spatially-dispersed liquid water was observed under the rib, while liquid water closed to the catalyst layer was identified in the conventional MEA (Fig.2(c)). At high current density operation (1.2A cm-2), liquid water in the MEA with VGCF was still accumulated closed to the rib. These observations by soft X-ray radiography indicate that VGCF-MPL plays a role to guide liquid water removal in MEAs, which resulted in better cell performance, although physicochemical properties of VGCF-MPL should be unveiled in the future.This work has been supported by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.