Toshinari Araki

Natural gas storage in activated carbon pellets without a binder

Abstract Activated carbon pellets without a binder from cellulose microcrystals as a raw material were investigated. After compression of the raw materials, the thus obtained raw material pellets were slowly carbonized to 1073 K under nitrogen. To activate them, the carbon pellets were heated to 1173 K under carbon dioxide. The activated carbon pellet shape, after heat treatment, was columnar by using the previous employed compression of the raw material. The total surface area, pore volume, and average pore diameter for all the samples were evaluated from the analysis of N2 adsorption isotherm data. The total surface area and the pore volume were decreased with an increase in compression pressure under the same heat treatment conditions. On the contrary, the bulk densities of the activated carbon pellets were increased. However, these properties can be easily controlled by changing the sintering temperature and time. The bulk density of sample pellet was 0.56 g/cm3. It is 2.3 times higher than activated carbon powder, which was made without the compression process. The total methane storage capacity at 298 K reached 164 cm3 in 1 cm3 volume of activated carbon pellets at 3.5 MPa.

Development of a Precisely Temperature Programmable Langmuir Trough for Measuring Properties of Insoluble Monolayers at the Water Surface as Functions of Temperature.

A new type of Langmuir trough was constructed in which temperature of the water surface is controlled precisely according to a program using a large number of Peltier elements and a microcomputer. We can suppress convection of the water in the trough during linear heating or linear cooling by planning the trough as thin as 2 mm. This trough is very suitable for measuring A-T isobars and π-T isochores of insoluble monolayers which are rarely measured precisely. The newly developed trough can permit observation of Brewster angle microscopic (BAM) images of insoluble monolayers clearly during measurements of A-T isobars by suppressing convection completely.

Transition to three-dimensional structures in monolayers of a series of long-chain acids on the water surface by compression studied by transmission electron microscopy and atomic force microscopy

Abstract Insoluble monolayers of long-chain acids at the water surface are unstable above their equilibrium spreading pressure (ESP). They exhibit pressure relaxation at a constant area or area relaxation at a constant pressure. The main cause of these relaxations for insoluble monolayers is the formation of three-dimensional structures at higher surface pressures by compression. The shape of π- A isotherms of a series of long-chain acids measured for a constant observation time at 10 °C changed systematically with changing chain length. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) observation of one-layer samples deposited onto cover glass revealed that there are two kinds of three-dimensional structure. The nucleation and growth mechanisms of these three-dimensional structures are proposed from the TEM and AFM images.

Structural characterization of phthalocyanine Langmuir—Blodgett multilayer assemblies by FT-IR spectroscopy

Abstract Structural characterization of tetrakis (dimethyldioctadecylammonium) nickel phthalocyanine tetrasulfonate (Pc4) Y-type Langmuir—Blodgett (LB) films with 1-, 2-, 3-, 4- and 10-monolayers has been made by Fourier-transform infrared (FT-IR) transmission, reflection—absorption (RA), and polarized transmission spectroscopy. The following conclusions can be obtained from the above measurements: (i) The hydrocarbon chains of Pc4 in the LB films are in a hexagonal or analogous (pseudohexagonal) subcell packing and take an uniaxial orientation with respect to the surface normal. (ii) The hydrocarbon chains are inclined to a considerable extent with respect to the surface normal while the Pc plane is oriented nearly perpendicular to the surface in the LB films. (iii) The structure and molecular orientation of the Y-type LB films with the first layer in the “head-on” configuration and those with the first layer in the “tail-on” configuration are very similar to each other.

FURTHER INVESTIGATION OF THE PREPARATION PROCESS OF POLY(P-PHENYLENEVINYLENE) LANGMUIR-BLODGETT FILMS

Abstract The Langmuir-Blodgett (LB) films of conducting poly( p -phenylenevinylene) (PPV) were prepared by thermal treatment (250°C, 1 Torr) of the LB film of the PPV precursor, amphiphilic poly( p -xylylene-σ-diethylsulphonium) salt with perfluorononanoate counterion. The formation of the π-conjugated PPV structure varied with the thermal annealing time and was studied by means of UV spectroscopy. The elimination of the sulphide and fluorinated fatty acid during the thermal treatment was determined quantitatively by X-ray photoelectron spectroscopy. Both results indicated that extension of the π-conjugated structure could be realized and conversion from the PPV precursor to PPV could be completed within 10 min under these conditions. Furthermore, transmission electron microscopy examination revealed a gradual change in the surface image from heterogeneous to homogeneous during the thermal treatment, which indicated that a smooth surface of the PPV LB film was gradually formed by the thermal conversion.

The time of observation of π−A isotherms III. Studies on the morphology of arachidic acid monolayers, observed by transmission electron microscopy of replica samples of one-layer Langmuir-Blodgett films using plasma-polymerization

Abstract An idea regarding the time of observation for measurement of π−A isotherms of monolayers is proposed. Only π−A isotherms measured for the same “times of observation” can be compared directly with each other. Transmission electron microscopic (TEM) observation of replica samples of one-layer LB films of archadic acid reveals that there are two kinds of three-dimensional structures in the collapsed films: platelet crystallites of the order of a few thousand nanometers and large numbers of granular structures of the lateral order of several tens of nanometers with a height of about 5 nm. By comparing the πminus;A isotherms of a series of long-chain acids (C22, C20, C18, C16 and C15), measured for the same “time observation” and their TEM images, it is estimated that the granular structures are all generated simultaneously after some induction period following the collapse of the monolayers.

Attenuated total reflection/FT-IR studies on Langmuir-Blodgett films of 3-octadecyl-2-[3-(3-octadecyl-2-benzothiazolinylidene)-1-propenyl] benzothiazolium iodide

Abstract Attenuated total reflection (ATR)/Fourier transform infrared (FT-IR) spectra have been measured for Langmuir-Blodgett (LB) films of 3-octadecyl-2-[3-(3-octadecyl-2-benzothiazolinylidene)1-propenyl] benzothiazolium iodide (NK-2560) deposited on a germanium plate with various monolayers. The spectra obtained are very close to the IR transmission spectrum of 3-ethyl-2-[3-(3-ethyl-2-benzothiazolinylidene)-1-propenyl]benzothiazolium iodide (NK-76) in the powdered microcrystalline state which is thought to take conformation A. This observation implies that NK-2560 assumes conformation A in the LB assemblies. The LB film spectra are, however, slightly different from IR transmission spectra of NK-2560 in the solid states (powdered microcrystalline and KBr disc) in that IR bands due to C C and C C stretching modes of the central conjugated system show an upward shift by 7–99 cm −1 in the former compared with the latter. This result can be interpreted by assuming that the electronic structure of the central conjugated system of NK-2560 is significantly different between the LB films and the solid states. A comparison of the ATR/IR spectra of the 1-monolayer LB film with “head-on” configuration and that with “tail-on” configuration shows that NK-2560 molecules have highly ordered ( trans -zigzag) hydrocarbon chains in the former film, but in the latter film they have much less ordered hydrocarbon chains.

Preparation and Evaluation of Polyaniline Lb Films

The mixed Langmuir-Blodgett (LB) films of polyaniline and stearic acid were successfully prepared. They formed stable monolayers at the air-water interface and could be deposited onto solid substrates as Y-type films using a usual LB technique. The stearic acid was removed from the LB films by either immersing the films in organic solvents or heating the films under reduced pressure. The replica method coupled with transmission electron microscopy (TEM) confirmed that these treatments were useful for the preparation of smooth films. The spectroscopic measurements proved perfect removal of the stearic acid after the treatment in solvent. Different electrochemical properties were observed for two kinds of the LB films by cyclic voltammetry

Morphology and molecular orientation and structure of Langmuir–Blodgett films of chlorophyll a studied by atomic force microscopy and UV–VIS and IR spectroscopies

Atomic force microscopy (AFM), scanning electron microscopy (SEM) and UV–VIS absorption and IR spectroscopies have been used to investigate the morphological and molecular structure of Langmuir–Blodgett (LB) films of the title compound (Chl-a). The AFM and SEM measurements reveal that the surface of the LB films are very smooth and consist of rigid and condensed monolayers. The tilt angle of the chlorin plane in a six-monolayer LB film of Chl-a has been calculated to be 35° between the normal of the chlorin plane and the substrate normal and 44° between the dipping direction and projection of the normal of the chlorin plane, from measurements of its polarized UV–VIS spectra. Band frequencies in the 1750–1400 cm −1 region of the IR spectra of one-, six- and ten-monolayer (ML) LB films of Chl-a suggest that Chl-a exists in a five-coordinated monomer in the films, irrespective of the number of monolayers. Comparison of IR transmission and reflection–absorption spectra of 6 ML LB films of Chl-a indicates that the chlorin plane and the ester and keto CO groups are tilted considerably with respect to the surface normal. LB films of pheophytine a (Phe-a) have also been studied for comparison. Comparison of the UV–VIS and IR spectra of the LB films of Chl-a and Phe-a show that pheophytinization occurs little in the LB films of Chl-a. High-performance liquid chromatography (HPLC) examination has supported this conclusion. All the experiments carried out in the present study suggest that Chl-a molecules in the LB films are oriented in an orderly manner with face-to-face packing of the chlorin rings.

Comparison of Langmuir-Blodgett films of polyamic acid tert-amine salts with single, double and triple chains

Abstract Characterization of the Langmuir-Blodgett (LB) films of polyamic acid tert-amine salts (3a–3c) containing single, double and triple chains, and polyimide (4) was carried out. The LB films obtained from the monolayers for 3b and 3c showed X-ray diffraction peaks, whereas these peaks were not observed for 3a. The d spacings and diffraction intensity of LB films for 3b transferred from the expanded phase increased with time after deposition and increasing deposition pressure, and their values approached those obtained for films transferred from the condensed phase. On the contrary, the LB films for 3c displayed a constant d spacing of 5.4 nm, irrespective of whether they were built up from the expanded phase or from the condensed phase. The thickness of LB films was estimated from X-ray interference, X-ray diffraction methods and observation of micrographs, and the monolayer thicknesses obtained were in fairly good agreement with one another.