Polymer materials have received much attention from a wide range of industrial interests. Functional fillers are often introduced to polymers to add new functions that the pristine polymer materials show inferior values. As for thermal conductivity (TC), thermal conductive fillers such as ceramics, functional nanocarbons, and metals are often used. Among the polymers used in industrial fields, polyimide (PI) has excellent thermal stability and solvent resistance. However, the TC of PI is low as is often the case in other commonly used polymers. In the present paper, PI-based composite materials were reviewed from the viewpoint of TC. Hexagonal boron nitride, aluminum nitride, graphene, graphene derivatives (graphene oxide, reduced graphene oxide) and carbon nanotubes were the focus as representative thermal conductive fillers.

The global increase in energy consumption has caused serious environmental problems, especially CO₂ emissions. In general, CO₂ is produced from the combustion and oxidation reactions at high temperature. The use of thermochemical energy storage is considered an appropriate approach to enhance the utilization of surplus or waste heat from high temperature industrial processes. So far, there are very few reports that have been published for high temperature thermochemical energy storage. In this study, high temperature thermochemical energy storage based on the lithium orthosilicate/carbon dioxide (Li₄SiO₄/CO₂) reaction was developed. A new candidate storage material was fabricated with four different concentrations of the potassium carbonate (K₂CO₃) additive (0, 6, 11, 17, and 33 mol%), in the shape of pellets, from the point of energy density view. On the basis of the results of the carbonation and decarbonation experiments, the highest thermal output and storage densities were recorded for a pellet possessing a 11 mol% concentration of the K₂CO₃ additive. Furthermore, this pellet, LK11, showed cyclic ability with repeat reactions over twenty cycles. Thus, LK11 pellet can be used as a thermochemical storage material because of its ability to store and release heat at high temperatures, ranging from 550 to 700°C.

The present work investigates the hydration reaction of a composite made up of β-lanthanum sulfate and thermally expanded graphite for possible use as a chemical heat storage technique for exhaust heat below 250°C. The effects that water concentration and hydration temperature exert on hydration behavior were mainly studied via the use of a disk-like pelletized sample with a β-lanthanum sulfate content of 98 wt%. These effects were experimentally investigated using a thermal-gravimetric apparatus. The maximum hydration rate increased as the water vapor concentration increased under a hydration temperature of 110°C. Moreover, the maximum heat power density was 2.1 MW/m³ at a water vapor concentration of 17.5 mol/m³. Furthermore, the near-final values of the hydration numbers that were found at 30 min decreased as the hydration temperature increased to a range of from 110 to 180°C. In the initial stage, however, hydration rates were not dependent on temperature under the present experimental conditions. The temperatures inside the pelletized samples during hydration were also measured. These temperatures drastically increased immediately after the start of hydration regardless of the beginning temperature. For instance, a maximum value of 195°C was obtained at a hydration temperature of 130°C with a water concentration of approximately 17.1 mol/m³.

In order to improve the performance of Lithium-ion secondary batteries (LiBs) for electric vehicles and hybrid electric vehicles, it is very important to understand the internal transport phenomena and resistance under a high rate condition to increase power density. Especially, it is important to focus on the actual porous electrode structure, and the Li ion and electron conductivity have to be evaluated by the effective conductive path with the actual electrode material properties. Thus, the numerical simulation of electrochemical reaction and mass transport in the electrode layer are needed to design a heterogeneous porous structure which consists of active material, conductive material and binder. Then, the values of parameters in this model are essential for accuracy of it. However, some parameters cannot be measured precisely in experiment, especially, reaction rate constant, tortuosity of the separator, Li⁺ diffusion coefficient, and transport number in the electrolyte are treated as literature values or ex-situ results. In this study, we established a method of identifying these parameters by using experimental data in various conditions and a complex method. Further, this approach was applied to 1D LiB simulation. Fitting the experimental data of some SOC and some discharge rate conditions was carried out. Additionally, RMSE (Root Mean Square Error) to judge this fitting was evaluated. From these results, it was concluded that the parameters can be identified. In addition, with the identified parameters, the optimal electrode structure for a high-output power density cell was designed automatically.

Due to their high theoretical energy density, lithium-air batteries (LABs) are expected to become the standard secondary battery system of the next generation. However, for practical usage, their cycle performance needs to be improved. Thus far, few studies have investigated how the structure of carbon cathode materials affects their cycle performance. In this study, meso- to macro-porous carbon gels (CGs) heat-treated at different temperatures were prepared, and were used as model materials to discuss the relationship between carbon structure and cycle performance. Nitrogen adsorption experiments, X-ray diffraction analysis, Raman spectroscopy analysis, and thermal gravimetric analysis were conducted to derive the pore structure, crystal structure, carbon bonding state, and oxidation resistance of CGs, respectively. In addition to standard analysis methods, temperature program desorption measurements were conducted under vacuum to aid the analysis of surface oxygen-containing functional groups. Charge–discharge measurements indicated that cycle performance improves when the carbons were heat-treated at higher temperatures. Functional groups on the carbon surface were found to promote side reactions and reduce reversible capacity. Defects in the carbon are thought to promote uneven deposition of deposits which tend to cause the sudden “death” of LAB.

The effective addition of surface oxygen groups, which are active sites for redox reactions, on carbon clothes as electrodes by electron beam irradiation in normal air which contains environmental humidity, dry air, or nitrogen atmosphere was carried out. The irradiation introduced 20 at% oxygen at the carbon surface as determined by X-ray photoelectron spectroscopy and the phenol-type hydroxyl group, the carboxylic group, etc., were detected by temperature-programmed desorption. Single-cell measurements indicated the current density at 1.3 V_{-IR-corrected} of the irradiated electrode in normal air was 28% higher than that of the as-received electrode. Since double-layer capacitance between the as-received carbon cloth and irradiated carbon cloth in normal air was similar, the improvement of current density is attributed to the increase of surface oxygen groups. In addition, the radiation in both normal air and dry air improved electrochemical activity similarly. This result suggests the radiation-chemical reaction in this study is dominated by the oxidation reaction with ozone or nitrogen oxides (NO_x), while in the meantime, the contribution of the hydroxyl radical from water is considered to be negligible.

In order to accelerate the development of polymer electrolyte fuel cells (PEFCs), it is important to optimize the structure of catalyst layers (CLs) including Pt particles, ionomer loading, and porosity, resulting in the improvement of performance. Numerical analysis can assist in designing the optimized CLs without trial and error. In this study, the effects of silica-coated Pt catalysts (SiO₂/Pt/C) were investigated by experimental measurements and numerical analysis in order to obtain manufacturing guidelines by designing optimized CLs for PEFCs. In the experimental results, the SiO₂/Pt/C showed lower performance than non-coated Pt catalysts (Pt/C) under relative humidity (RH) of 80% at 80°C. In the case of the SiO₂/Pt/C, the addition of two parameters including the enhancement of proton conductivity and an increase in the oxygen diffusion resistance in the CLs, attributed to silica layers, were considered. The distribution of current density at 0.8 A cm⁻² of the SiO₂/Pt/C at each humidity condition (100%RH, 80%RH, 60%RH, 40%RH) is more homogeneous and reached closer to the gas diffusion layer compared to those of the Pt/C. The result indicates that it is possible to improve durability by increasing the reaction located near the polymer electrolyte membrane. For both catalysts, the overvoltages at 0.8 A cm⁻² were similar to each other, except for that of proton resistance in ionomer and oxygen diffusion in the ionomer.

This study reports on direct formate fuel cell (DFFC) operation using non-precious metal (NPM) as the cathode catalyst. Iron- and cobalt-nitrogen-doped carbon nanotube (Fe-NCNT and Co-NCNT) were synthesized by pyrolysis of multiwalled carbon nanotubes, metal precursor and nitrogen precursor. These NPM catalysts showed high fuel tolerance in acidic medium, but the fuel tolerance in alkaline medium remains unclear. Herein, we determine the formate tolerance on the NPM catalysts and commercial Pt/C catalyst in alkaline medium. The DFFC performance test was conducted and the results compared with the direct formic acid fuel cell (DFAFC) reported in our previous work. The oxygen reduction reaction (ORR) activity and the formate tolerance on the NPM catalysts were evaluated by rotating disk electrode (RDE) in alkaline medium. Both NPM catalysts showed lower ORR activity than the Pt/C catalyst, but they exhibited higher formate tolerance than the Pt/C catalyst. Comparing the single-cell performance under various HCOONa concentrations, DFFC with Co-NCNT catalyst showed higher maximum power density than with Pt/C catalyst with 2 M KOH containing 4 M and 6 M HCOONa due to its higher formate tolerance. Therefore, it is considered that the NPM cathode is available for high concentration operation of DFFC. However, DFFC with Fe-NCNT and Co-NCNT cathode catalyst exhibited the highest maximum power density of 39.7 mW cm⁻² and 89.8 mW cm⁻², respectively, at 60°C with optimal fuel concentration, i.e. 2 M KOH containing 4 M HCOONa. These performances were lower than that of DFFC with Pt/C cathode catalyst at optimal fuel concentration, i.e. 2 M KOH containing 2M HCOONa. Considering the fact that the power density of DFAFC (acidic condition) using NPM catalyst was higher than that with Pt/C catalyst at optimum fuel concentration, the NPM catalysts are more preferable for the acidic condition than the alkaline condition.

The present study investigates porous carbon black aerogels fabricated with polyvinylidene fluoride (PVDF) as binder and N-methylpyrrolidone (NMP) as solvent and dispersant, and dried by supercritical drying using CO₂ at 20 MPa and 40°C, which resulted in greater porosity and thickness than aerogels prepared by evaporative drying. Increasing the ratio of solvent in carbon black slurry increased the porosity and thickness and decreased electrical conductivity. The electrical conductivity of aerogels prepared at 60°C is higher than aerogels prepared at 40°C. However, aerogels prepared at 80°C are broken because evaporative drying occurred simultaneously, whereby the conductivity reduced. Porous carbon nanofiber aerogel made by supercritical drying using CO₂ at 20 MPa and 40°C had porosity as high as carbon black aerogel. However, its electrical conductivity is less than carbon black aerogel because of the net-like structure which has less touch points between the fibers compared to carbon black particles which gather together and have more touch points between the particles. A coin cell consisting of porous carbon nanofiber aerogel or electrode, lithium and electrolyte was connected with oxygen and carbon dioxide at the ratio of 1 : 1. Regardless of its low electrical conductivity, the carbon nanofiber electrode showed superior electrical capacity. It also withstood 10 cycles, whereas the carbon black electrode could not withstand 10 cycles.

Herein, the CO₂ capture performance of a thermal swing adsorption (TSA) process, equipped with adsorbent-packed heat exchangers, was investigated taking the effective use of waste heat into account. Two typical CO₂ adsorbents—CaA and NaX zeolites—were examined with regard to their CO₂ adsorption properties from a simulated dry exhaust gas containing 9.5 vol% CO₂ and 90.5 vol% N₂. The effects of the hot water temperature supplied to the adsorber and the regeneration air flow rate on the separation performance were investigated, as a function of the adsorption/desorption switching time. Increasing the regeneration temperature was observed to improve the separation performance, and a regeneration temperature of 80°C, yielded a five-fold increase in the CO₂ concentration when compared with the feed gas at the optimal adsorption/desorption switching interval. A TSA process incorporating an adsorbent-packed heat exchanger is evidently an effective means of enriching CO₂, based on decreasing the regeneration of air by internal heating and removal of heat by internal cooling. The separation behaviors of both zeolites are similar, except that the CO₂ concentration in the desorbed gas and the recovery ratio of CaA, at a shorter adsorption/desorption interval, was somewhat larger than that of NaX. These findings suggest that the adsorption rate of CaA is largely dependent on the adsorbed uptake volume. Reducing the regeneration air flow rate to one fortieth of the original value further increased the CO₂ concentration at the desorption outlet, while lowering the CO₂ recovery ratio. Additionally, the time profiles of desorption outlet gas volume and CO₂ concentration indicated that the desorption outlet CO₂ concentration momentarily reached >70%. Furthermore, the findings also clarified the rapid desorption rate of the adsorbed N₂, which was almost completed within the initial desorption period, and which decreased the averaged CO₂ concentration over the regeneration period.

The present study investigates the treatment of palm oil mill effluent (POME) with a dielectric barrier discharge (DBD) plasma system. This paper presents the results of the yield of hydrogen (H₂) and methane (CH₄), and the removal of organic matter and chemical oxygen demand (COD) from POME. Also, state-of-the-art methods were employed to measure methane and hydrogen directly from the reactor as well as their improvement. The DBD was carried out with an applied voltage of 10–25 kV in a batch glass plasma reactor. The results revealed a significant effect of the voltage variation on the yield of H₂ and CH₄. Increasing the applied voltage enhanced the conversion of POME with COD reduction in the range of 48.9 to 53.7% and biochemical oxygen demand reduction in the range of 30 to 40% when the applied voltage was 15–25 kV. Furthermore, to estimate the removal of organic matter in POME, a fluorescence excitation-emission matrix was used.

Silica hybrid membranes have been developed for a membrane reactor for a propane dehydrogenation (PDH) reaction using a counter diffusion chemical vapor deposition (CVD) method. The effects of the alkyl chains in the silica precursor were investigated to control the membrane properties. Membrane reactor tests using a CVD silica membrane were performed. An ethyltrimethoxysilane (ETMOS)-derived membrane deposited at 500°C showed a high H₂/C₃H₈ selectivity of 650. The C₃H₈ conversion was 53% with C₃H₆ selectivity of 69% for the 600°C reaction in the membrane reactor. The conversion was slightly higher than that at equilibrium.

We fabricated carbon nanoparticles in a series of pulsed laser ablation (PLA) experiments with a graphite target using an Nd:YAG laser. The carbon nanoparticles were synthesized in a supercritical carbon dioxide (CO₂) medium at various temperatures and various pressures. We also investigated the effect of CO₂ pressure (density) on the morphology of the fabricated nanocarbon particles under isothermal conditions at 308 K or maintaining a constant medium density. The carbon particles generated under the supercritical condition in the vicinity of 8 MPa exhibited a spherical shape with a peak diameter range of 20–30 nm. Some of the generated particles had a nano-crystalline, regular structure. The lattice spacings of these single crystals were 0.20 nm and 0.37 nm, which corresponded to lattice spacings of diamond and graphite, respectively. The diffraction pattern of a selected area of the samples confirmed that the synthesized fine particles had a cubic-diamond crystal structure. The coarse particles, meanwhile, had a regular hexagonal-graphite structure. Raman spectroscopy of the synthetized nanoparticle samples revealed a phase transition from an amorphous structure to a mainly graphite structure in association with changes of the isobaric specific heat capacity of the supercritical CO₂. The temperature distribution profile in the plasma plume was presumed to have affected the crystalline fraction of the generated carbon nanoparticles.