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In the present study, by a simple method, carbon soot with a narrow absorption features at around 220 nm was produced by pyrolysis of methane gas at a hot (1400–2800 °C) filament. A detailed correlation between the structure and the optical spectra of carbon soot was carried out using a high-resolution transmission electron microscope. It appears that the origin of the narrow absorption peak is an onion-like graphitic structure. Interestingly, we found that the absorption peak position and the size of the soot can be controlled by the production temperature. The absorption peak is located at 217.5 nm, i.e., at the position of an intense interstellar absorption, when the onion structure has about 5 nm diameter. Infrared spectroscopy was applied to further elucidate the chemical composition of the obtained soot. [Copyright &y& Elsevier]

Titanium metal powder mixed with 2–5.5 wt.% iron powder was flowed on Ar gas stream and evaporated in the RF plasma with gas mixture of Ar and O2. The spherical iron doped TiO2 powder with colour of pinkish white was obtained. Transmission electron microscope (TEM) analysis of the doped particles showed the periodic planer arrangement of iron atoms at empty space of TiO2 crystals. In the case of Al doped particles, the lattice image presenting the mosaic-like structure is predominantly seen at the (110) lattice image. The difference of the segregation of Fe and Al in rutile particles has been discussed as the intrinsic nature of Fe and Al atoms. [Copyright &y& Elsevier]

Abstract: In this study, we investigated the effects of humidity and oxygen reduction on the degradation of the catalyst of a polymer electrolyte membrane fuel cell (PEMFC) in a voltage cycling test. To elucidate the effect of humidity on the voltage cycling corrosion of a carbon-supported Pt catalyst with 3nm Pt particles, voltage cycling tests based on 10,000 cycles were conducted using 100% relative humidity (RH) hydrogen as anode gas and nitrogen of varying humidities as cathode gas. The degradation rate of an electrochemical surface area (ECSA) was almost 50% under 189% RH nitrogen atmosphere and the Pt average particle diameter after 10,000 cycles under these conditions was about 2.3 times that of a particle of fresh catalyst because of the agglomeration of Pt particles. The oxygen reduction reaction (ORR) that facilitated Pt catalyst agglomeration when oxygen was employed as the cathode gas also demonstrated that Pt agglomeration was prominent in higher concentrations of oxygen. The ECSA degradation figure in 100% RH oxygen was similar to that in 189% RH nitrogen. It was concluded that liquid water, which was dropped under a supersaturated condition or generated by ORR, accelerated Pt agglomeration. In this paper, we suggest that the Pt agglomeration degradation occurs in a flooding area in a cell plane. [Copyright &y& Elsevier]

- Exothermic reactions during the annealing of laboratory synthesized amorphous magnesium-bearing silicate particles used as grain analogs of cosmic dust were detected by differential scanning calorimetry (DSC) in air. With infrared spectroscopy and transmission electron microscopy, we show that cosmic dust could possibly undergo fusion to larger particles, with oxidation of magnesium silicide and crystallization of forsterite as exothermic reactions in the early solar system. The reactions begin at approximately 425, approximately 625, and approximately 1000 K, respectively, and the reaction energies (enthalpies) are at least 727, 4151, and 160.22 J g−1, respectively. During the crystallization of forsterite particles, the spectral evolution of the 10 μm feature from amorphous to crystalline was observed to begin at lower temperature than the crystallization temperature of 1003 K. During spectral evolution at lower temperature, nucleation and/or the formation of nanocrystallites of forsterite at the surface of the grain analogs was observed. [ABSTRACT FROM AUTHOR]

Abstract: The formation process of MoO2 crystal from amorphous MoO3 film has been imaged by in situ observation with a transmission electron microscope. Selective growth of flower-shaped MoO2 crystals by heating above 673K in vacuum was directly observed. Since the MoO2 crystal has metallic conductivity of the order of indium oxide film containing tin (ITO film), the thin film growth of the MoO2 phase has been discussed on the basis of a new substitute for ITO film. [Copyright &y& Elsevier]

Abstract: Nanocrystallites formed with a magnetic field in gel have been examined by transmission electron microscopy. Micro-twin and multiply twinned nanoparticles of PbBr2 were selectively grown induced by the reaction under the influence of the magnetic field during the gel growth between Pb(NO3)2 and KBr solutions. The pentagonal growth in a magnetic field was discussed as a result of the attenuation of the ionic component in PbBr2 crystals. [Copyright &y& Elsevier]

Abstract: The synthesis of Al–Cr single quasicrystal (QC) nanoparticles of the decagonal phase was achieved by introducing an advanced gas flow evaporation method. By obtaining successive electron diffraction patterns for single-QC nanoparticles, the phase transformation temperature of a single-QC nanoparticle was determined to be 700°C. It was also determined that part of the QC nanoparticle decomposed into hex-Al8Cr5 and Al during the phase transformation. Since the grain growth did not occur during the phase transformation in the present experiment, the inherent phase transformation temperature could be measured. [Copyright &y& Elsevier]

Abstract: Tetragonal BaTiO3 particles less than 50nm in diameter have been produced by the gas evaporation method. The conventional gas evaporation of a powder of mixed TiO2 and BaCO3 and the gas flush evaporation of BaTiO3 powders have been performed. In the case of the evaporation of the mixed powder, the crystallization from the amorphous particles was observed. The preparation of a large amount of 20-nm-diameter BaTiO3 particles was achieved by the gas flush evaporation method. These particles showed the characteristic absorption at 18 and 23μm, which can be used for the identification of BaTiO3 nanoparticles. The nanosize particles also showed the characteristic absorption at 320nm in the ultraviolet region. [Copyright &y& Elsevier]

Abstract: Alterations of carbon particles carrying Pt clusters were studied by means of transmission electron microscopy (TEM). Carbon particles of size 20–30nm produced in a He gas atmosphere by the conventional arc-discharge method changed into carbon tubes or ribbon-like spherules based on an onion-like structure by heating in air at 300°C. In the case of carbon particles carrying Pt clusters, the alteration of carbon particles took place gradually at 300°C, and the Pt clusters become partially exposed to the air as they were no longer covered by the carbon layer. The generation of electricity by using Pt clusters in fuel cell is proposed as an application for the Pt clusters. [Copyright &y& Elsevier]

Abstract: Al–Mn quasicrystal ultrafine particles can be produced by the advanced gas evaporation method (AGEM), which is a method of preparing ultrafine alloy particles by coalescence growth among the particles near the evaporation sources. We investigated the phase transition temperature from a quasicrystal to a stable crystal, by examining successive electron diffraction patterns of an ultrafine particle in an in situ experiment using a transmission electron microscope. In spite of the report that the Al86Mn14 quasicrystal transforms into the crystal phase at around 400–670°C on thin film specimens, the quasicrystal ultrafine particle transformed at 800°C, i.e., the quasicrystal ultrafine particle is more stable. Since the cross-sectional view of the surface oxide layer of the quasicrystal ultrafine particles can be easily observed, the surface oxides of η-Al2O3 and MnO were characterized as a result of the oxidation of residual atoms on the surface of the produced alloy particles including the quasicrystals. The conditions required for Al–Mn quasicrystal ultrafine particle formation by the AGEM can be estimated under the cooling rate of 105K/s. [Copyright &y& Elsevier]

A recently developed experimental method of producing quantum dots covered with a carbon layer has been applied to Pt clusters to make carbon-coated materials. Pt clusters with the size of 1–5 nm embedded in carbon quantum balls with the size of 10 nm order have been produced by the advanced gas evaporation method in He gas at 10 kPa. The carbon layer covering Pt clusters was ∼3 nm in thickness. The stability and usefulness of electron emission as functional materials have been discussed with respect to the electron beam irradiation effect and contact potentials between the metallic cluster and carbon layer. [Copyright &y& Elsevier]

The structure of NiTi shape memory alloy nanoparticles was determined by high-resolution electron microscopy. The mixture of Ni4Ti3 and R-phases was observed, which clearly showed lattice relationships of (2 1¯ 1)B2//(1 0 1)Ni4Ti3 and (2 2¯ 0)B2//(1 3 1)Ni4Ti3. Lattice images of an R-phase particle suggested the existence of a Ni-rich Guinier–Preston zone (G.P. zone). [Copyright &y& Elsevier]

A particle with a CdTe core and carbon mantle was produced by the advanced carbon-coating method which enables direct coverage with a carbon layer using an electron microscope. The coagulated particles containing approximately 30–200 CdTe particles produced by the gas evaporation method were covered with a carbon layer of about 7 nm thickness at 300°C. By heating these particles above 500°C, the sublimation process of a part of the CdTe particle can be directly captured by high-resolution transmission electron microscopy and recorded in real time on videotape. Sublimation on the CdTe(1 1 1) surfaces occurred in the step flow mode of two (1 1 1) layers. It was observed that two (1 1 1) zinc-blende layers changed to the (0 0 0 2) wu¨rtzite configuration unit just before sublimation. The condensation of CdTe on the sublimated particle surface and growth of CdTe in the carbon layers were also captured in the video image. These sublimation processes were discussed in terms of the existence of the polarity of II–VI compounds. [Copyright &y& Elsevier]

In order to elucidate the stability of a silicon oxide layer on ZnO, the dynamic behavior of SiO- and SiO2-layer-coated ZnO ultrafine particle surfaces were directly observed by heating in a transmission electron microscope up to 700°C. In the case of SiO-coated ZnO ultrafine particles, ZnO nanocrystallites with the size of 2 nm grew in the SiO layer at 500°C. In the case of SiO2-coated ZnO ultrafine particles, β-cristobalite with the size of 10 nm order was grown at 600°C. Zn2SiO4 particles were grown by coalescence between β-cristobalite and ZnO at 700°C. By comparing the SiO and SiO2 layers on ZnO ultrafine particles, it was found that the behaviors of the two silicon oxide layers are clearly different. [Copyright &y& Elsevier]

The high-temperature behavior of Au clusters on a Si nanoparticle surface has been studied using the atomic-resolution high-temperature stage of a transmission electron microscope. Au atoms diffuse into the Si nanoparticle at 680°C and return to the surface at room temperature. The movement of diffused Au atoms on the Si surface steps and the movement of Guinier–Preston-zone-like contrast observed for the segregation of Au atoms on the (1 1 1) Si plane, have been directly observed. These phenomena, which can be detected only at high temperatures, are presented in this paper. [Copyright &y& Elsevier]

Dynamics of crystallization of amorphous antimony-selenium film deposited on carbon substrate have been studied by the high-resolution transmission electron microscopy. The amorphous film was suddenly crystallized at 200°C by heating in vacuum. By the electron beam irradiation crystallization occurred at the focused electron beam region in the amorphous film. The growth process of crystallization by electron beam irradiation was recorded on a video image at the atomic resolution mode. The growth front of crystallization showed nano-concave and -convex shapes. The recrystallization with the different orientation at the first grown crystal have been found, and discussed as the influence of remaining antimony crystallites at the first crystallized film region. [Copyright &y& Elsevier]

The reduction process of tenorite whiskers grown on a copper mesh by heating in vacuum has been directly observed using a transmission electron microscope equipped with a real-time video-recording system. The coating of the carbon layer and reduction of the tenorite whisker covered with a carbon layer have also been captured in real time on video images. The growth process of an amorphous carbon tube has been elucidated. [Copyright &y& Elsevier]

In order to elucidate the effect of synchrotron radiation (SR) irradiation on crystal growth, crystallization of WO3 films has been performed in vacuum under SR irradiation. The main results were compared with the results of heat treatment of the same film. Upon SR irradiation for 80 s using a toroidal mirror, a catastrophic change occurred, i.e. W3O crystals (A-15 type) with a size of less than 30 nm appeared. Decomposition of the WO3 film started at above 750 °C during vacuum heating. W, WO2 and incommensurate WO3 crystals appeared. W3O crystal produced neither intense electron beam irradiation nor vacuum heating. These results will be discussed in terms of the differences caused by excitation with a SR beam, i.e. strong inner shell excitation and ionization of W and O may have taken place. [Copyright &y& Elsevier]