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Additive manufacturing has attracted much attention as a new technology for producing lightweight and high-strength materials. The multi-phase-field method has been used in powerful numerical simulations to predict solidification microstructure formation in additive manufacturing. To verify the non-equilibrium multi-phase-field (NEMPF) model that can consider strong out-of-equilibrium solid/liquid interfacial conditions, the NEMPF model coupled with the CALPHAD-based thermodynamic database was used to simulate the solidification process in 316L stainless steel (SS) under a rapid cooling condition. The results show that interstitial carbon atoms tend to segregate at the solid/liquid interface, whereas no concentration gradient is observed at the grain boundary between the solid phases. Conversely, substitutional Cr, Mo, and Mn atoms were segregated in the solid grain boundaries. The effects of interfacial mobility and interfacial permeability on the solidification behavior were investigated. The results show that these parameters strongly influence the solidification rate and distribution of the solute concentration at the solid/liquid interface. [ABSTRACT FROM AUTHOR]

The effect of structure of organic additives on the electrodeposition behavior of Zn from alkaline zincate solution and its crystal morphology was investigated. Zn was electrodeposited on an Fe electrode at 20-1000 A·m-2, 2.4 × 104 C·m-2, 300K from unagitated zincate solutions containing the various organic additives as a leveling agent. The suppression effect of additives on the charge transfer and diffusion of ZnO2 2- ions in Zn electrodeposition corresponded to the number of adsorption site per a straight chain molecule of polymer. The effect of polymer alone on the decrease in size of Zn platelets crystals was small, but the crystal size significantly decreased with coexistence of low molecular additive. The crystal size of deposited Zn decreased in spite of small suppression effect on Zn deposition, showing that the crystal size of deposited Zn doesn't depend on the overpotential for deposition. With coexistence of low molecular additive with polymer, the crystal of deposited Zn was fine regardless of kind of polymer even though Zn deposited at the diffusion control of ZnO2 2- ions. [ABSTRACT FROM AUTHOR]

Power devices, such as power conversion and control devices, with excellent performance and high efficiency, are essential to realizing a carbon–neutral society. Towards that goal, devices using wide bandgap semiconductors, such as SiC and GaN, are being developed. Because wide bandgap semiconductors can operate at higher temperatures than conventional Si devices can, packaging technology with high heat resistance is required to demonstrate their performance. Previously, we proposed a sinter bonding technique using Ni nanoparticles for die bonding, i.e., bonding semiconductor chips to substrates. We demonstrate that Ni could be bonded to Al by sintering in the air. Meanwhile, the structures of recently reported power devices contain surface electrodes with an Al–Ni interface. Our research on Ni nanoparticle bonding and the Al–Ni interface in recent device structures demonstrated that evaluating the changes in the Al–Ni interface at high temperatures is crucial to ensure long–term reliability for high–temperature operation of the devices. Therefore, the diffusion behavior of Ni/Al multilayer samples annealed in air or vacuum was evaluated using Auger electron spectroscopy. Furthermore, the effect of the natural Al oxide film at the Ni/Al interface was also investigated. The results revealed that in the Ni/Al2O3/Al structure, atmospheric heating induced interdiffusion of Ni and Al through the Al oxide layer and that the natural Al oxide layer acted as a barrier to diffusion during vacuum heating. [ABSTRACT FROM AUTHOR]

Copyright of Journal of the Society of Japanese Women Scientists / Nihon Josei Kagakusha no Kai Gakujutsushi is the property of Society of Japanese Women Scientists and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It was investigated whether the spherical electrolytic copper powder could be electrolyzed by adding polyethyleneimine (PEI) in the electrolytic solution. In order to identify the optimum electrolysis conditions for the electrodeposition of spherical copper powder, we investigated the effect of molecular weight of PEI, the amount of PEI added, the current density, and the cathode material on the morphology of electrolytic copper powder. The electrodeposited copper powder was analyzed with a scanning electron microscope, a laser diffraction scattering particle size distribution measuring device, and an X--ray diffractometer. It was found that the spherical copper powder can be obtained by electrolysis at 3000 A·m-2 scraping copper powder every 10 to 60 s in solution containing 0.126 mol·dm-3 Cu2+, 0.5 mol·dm-3 free H2SO4 and 1.0 g·dm-3 PEI with average molecular weight 10000. [ABSTRACT FROM AUTHOR]

To investigate the effect of polymer additives and chloride ions on the electrodeposition behavior and morphology of copper powder, the polarization curves were measured and constant current electrolysis of 300 A·m-2 and 500 A·m-2 was conducted in an electrolytic solution containing 0.079 mol·dm-3 of Cu2+ and 0.5 mol·dm-3 of free H2SO4 at 293K and 393K without stirring. Polyethylene glycol (PEG) and polyethyleneimine (PEI) were used as polymer additives. PEG and PEI had a suppressing effect on the electrodeposition of copper powder. The current efficiency for Cu deposition decreased with the addition of PEG and PEI. The addition of PEG decreased the average particle size of the copper powder, while PEI didn't change the average particle size. When Cl-coexisted with PEG, the suppressing effect on the electrodeposition of copper powder became even greater and the particle size of the copper powder became finer than when Cl- or PEG was added alone. [ABSTRACT FROM AUTHOR]

Copyright of Journal of the Japan Research Association for Textile End-Uses / Sen'i Seihin Shohi Kagaku is the property of Japan Research Association for Textile End-Uses / Sen'i Seihin Shohi Kagaku and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To investigate the effect of halide ions on the electrodeposition behavior and morphology of copper powder, the polarization curves were measured and constant current electrolysis of 300 A⋅m-2 and 500 A⋅m-2 was conducted in an electrolytic solution of 0.079 mol⋅dm-3 of Cu2+ and 0.5 mol⋅dm-3 of free H2SO4 at 293K and 303K without stirring. In the deposition of copper powder, Cl- had a promoting effect on the deposition of copper powder, while Br- and I- had a suppressing effect. The current efficiency for Cu deposition increased with the addition of Cl- and decreased with Br-. The addition of Cl- reduced the average particle size of the copper powder and grown dendrite-shaped branches and trunks, resulting in a lower tap density. On the other hand, when Br- was added, the average particle size and crystallite size of the copper powder became smaller, and the tap density also became smaller. With increasing Cl- concentration in solution, the current efficiency for Cu deposition increased, that is, copper deposition was promoted even in the diffusion rate-determining region of Cu2+ ions, showing that the deposition of copper powder was affected by the charge transfer process for Cu deposition. The change in morphology of Cu powder with halide ions is attributed to change of the charge transfer process. The deposition of Cu powder seems to proceed under a mixed rate-determining process of the diffusion of Cu2+ ions and charge transfer. [ABSTRACT FROM AUTHOR]

Electrodeposition of Zn was performed on an Fe electrode at a current density of 50-5000 A·m-2 and a charge of 4 × 104 C·m-2 in an unagitated zincate solution at 313K containing 0.62 mol·dm-3 of ZnO, 4.0 mol·dm-3 of KOH or NaOH, and organic additives. The effects of KOH and NaOH on the deposition behavior of Zn in solution containing organic additives and the microstructure of the deposits were investigated. In solution containing a quaternary ammonium cation (PQ) and a quaternary ammonium salt with a benzene ring (QA), the current efficiency for Zn deposition at high current density region of 1000 to 5000 A·m-2 to produce the glossy films was higher with KOH than that with NaOH. At high current densities above 1000 A·m-2, Zn deposition approaches the diffusion limitation of ZnO2 2- ions. With additions of PQ and QA, the diffusion of ZnO2 2- ions was significantly suppressed, and the degree of suppression was smaller with KOH than that with NaOH. The polarization resistance at 200 A·m-2 investigated by AC impedance revealed that the adsorption ability of PQ and QA onto the cathode was smaller with KOH than that with NaOH. Since the suppression effect of additives on the Zn deposition is smaller with KOH than that with NaOH, the current efficiency for Zn deposition at high current density region is larger with KOH. The upper limit of current density to produce the glossy films was smaller with KOH than that with NaOH, and the spongy thin films were partially observed on the platelets crystals obtained at high current density in KOH solution. The content of C resulting from the additives in deposited Zn was smaller with KOH. These phenomena are attributed to the adsorption ability of PQ and QA onto the cathode being smaller with KOH. [ABSTRACT FROM AUTHOR]

Extracorporeal membrane oxygenation (ECMO) is a respiratory or cardiac life support consisting of a vascular access cannula, a blood pump, and an artificial lung that removes carbon dioxide and adds oxygen. Venovenous ECMO is typically used for various forms of critical respiratory failure including severe pneumonia due to the new coronavirus, whereas venoarterial (VA) ECMO sees greater utilization in the patient with heart failure such as cardiac arrest or other clinical states in which cardiac dysfunction is a significant component of illness. The transference of gases occurs due to diffusion across the hollow fiber membranes packed in the module of the oxygenator. Emergence of microporous membrane tremendously enhanced gas diffusion, and currently microporous membrane with a dense layer on the blood-contacting surface is widely used for longer period of usage over weeks. As the usage period for respiratory failure is getting longer, development of more durable ECMO system is required in the future. [ABSTRACT FROM AUTHOR]

Liesegang phenomenon has been extensively studied experimentally and theoretically in the field of nonlinear science. However, there are few studies for its applications due to the high nonlinearity. The particles produced with the Liesegang phenomenon have been limited to microparticles of sparingly soluble salt for many years. In this study, in anticipation of more engineering application of this phenomenon, gold nanoparticles are synthesized by diffusing gold ions into a gel containing a reductant. At that time, we investigate the influence of diffusion conditions on particle formation. As a result, we found that the size of resultant particles depends on the gel position. Furthermore, we construct mathematical model expressing ion diffusion and particle growth based on Ostwald ripening to discuss the particle formation mechanism. [ABSTRACT FROM AUTHOR]

In this work, Cr diffused Sm2Fe17Nx core-shell magnetic powders were prepared by reduction-diffusion (RD) process. Sm2Fe17 coarse, Cr2O3 and Sm2O3 fine powders were pulverized and mixed by ball milling, and the mixed powder was heat treated following Ca addition. Cr can diffuse into Sm2Fe17 powder above 875°C in RD process, and the diffusion distance of Cr increased with increase in RD temperature. Cr diffusion distance into Sm2Fe17 powder was about 1.1-1.2 μm under RD temperature at 875°C for 1.5 h, and the Cr-diffused Sm-Fe core-shell fine powder was obtained. After nitriding and washing, Cr-diffused Sm-Fe-N fine core-shell powder was successfully obtained, and the coercivity and saturation magnetization of the core-shell powder was 855 kA•m−1 and 122 Am2•kg−1, respectively. The saturation magnetization was higher than non-core-shell Sm-Fe-Cr-N powder. [ABSTRACT FROM AUTHOR]

LiFePO4 has attracted attention as a promising cathode material for lithium ion battery, because it consists of abundant elements. However, the battery performance of this material is limited by its low electron conductivity and low lithium ion diffusion rate. Coating its surface with an electronically conductive material, such as carbon, is one of the major methods to overcome this issue. In this study, we tried to synthesize Au nanoparticles (NPs) on the surface of carbon-coated LiFePO4 (LiFePO4/C) using sonochemical reaction to further enhance the electron conductivity. The size of Au NPs deposited on the surface of LiFePO4/C changed in relation to the concentration of Au ions. The battery performance of the Au NPs-deposited LiFePO4/C, as evaluated at a high constant current rate of 20 C, showed an improvement in the polarization and discharge capacity of LiFePO4/C. [ABSTRACT FROM AUTHOR]

By using the millimeter-wave or a kind of microwaves with short wave length, fabrication of ceramics with uniform morphology and examples of low temperature rapid sintering have been reported. Since the sintering progresses from the interior even with the rapid temperature increasing, it has been found that pores do not easily remain in the interior even if pressure sintering is performed afterwards, and the thermal conductivity of the heat radiation substrate is improved. We also reported diffusion promotion of cations which seems to contribute to the short-time sintering. We found zirconia ceramics having a composition which is easy to process using its plastic deformation during millimeter-wave heating and has creep resistance at elevated temperature with conventional heating. We have found improvement of oxide ion conductivity under irradiation with millimeter-waves in various added zirconia, ceria and LaGaO3 based ceramics and improvement of power generation properties of solid oxide fuel cells using these materials as an electrolyte. Improvement of mass transfer including diffusion was more pronounced in ion species with large millimetre-wave absorption, but it could not be explained by this alone, and comprehensively explained by non-thermal effect [ABSTRACT FROM AUTHOR]

Highly accurate measurement of thermal properties, reaction rates and mass transiers is necessary to grasp thermal flow characteristics of nuclear reactor plant because these properties are unsteadily sensitive to concentration, temperature, pressure and scale. On the real scale of the plant, however, there are problems such as the complexity of three-dimensional flow and the effect of convection. In this study, a novel technology that measures mass transfer and reaction rate of nuclear application material with high accuracy and high speed by applying microchannel which makes one-dimensional laminar flow, has developed. In this paper, a micro flow control system that can adjust flow with a minimum volume of 1µL/min. by a pressurized pump, was fabricated. In order to observe concentration diffusion of the flow field in real time, a near infrared spectroscopic visible observation device was developed and combined with the flow system. The mutual diffusion coefficient was measured for hydrazine hydrate, which is added for the purpose of preventing corrosion of secondary piping in nuclear power plant. It revealed that the absorption depends on the concentration near 1555 nm for Fourier transform near-infrared spectrophotometer. The diffusion coefficients of 5,10 and 20 wt% for hydrazine hydrate were quantified with the luminance profiles in the absorption peak wavelength. [ABSTRACT FROM AUTHOR]

HIP is a technology to simultaneously apply high pressures and temperatures to processed products by gas. HIP equipment applying HIP technology is used as an indispensable technology for densification of sintered products, removal of pores in casting and diffusion bonding of dissimilar materials. In this article, we will explain the history of the development of HIP equipment in Japan, then the introduction of new technology of the rapid cooling method and the HIP equipment with enhanced gas recovery capacity, aiming at productivity improvements of the HIP process, both of which were newly developed by our company. [ABSTRACT FROM AUTHOR]

In recent years, CCS (CO2 Capture and Storage), which capture CO2 from CO2 emission source and storage it in ocean, for mitigation of global warming has been expected. Especially, the method using depression region in seabed that can be stored huge amount of CO2 and reduce the influence on surrounding environment is required to practical use. In this method, hydrate is formed at the interface of liquid CO2 and seawater, but the diffusion behavior of CO2 with the hydrate film is not clear. Therefore, this paper aimed to measure CO2 concentration distribution and estimate effective diffusion coefficient. We visualized pH distribution in timeseries using bromophenol blue as a pH indicator in a pressure resistance visualization apparatus under hydrate formable conditions. As a result, pH concentration in water due to CO2-dissolving was verified by variation of colors of water including pH indicator, and saturated solution of CO2 represents pH 2.9. The diffusion process of CO2 was evaluated by calculated line of pH 3.0 from diffusion equation with the hydrate. We compared the experimental results and calculated results from diffusion equation, and the calculated results with larger diffusion coefficient than the conventional knowledge corresponds with experimental results. We compared experiment results with calculation results estimated by the diffusion equation of surface renewal model and small eddy model, and we confirmed that acceleration of diffusion can be explained by these models.

To improve the coefficient of performance (COP) in air-conditioning systems, the liquid-solid phase change temperature of the cold energy storage material should be approximately 10°C. Tetra-n-butyl ammonium bromide (TBAB) clathrate hydrate possesses the qualities of an efficient cold storage material. TBAB aqueous solutions form a clathrate hydrate at temperatures between 5 and 12°C, depending on the concentration. The temperature region is well suited to air conditioning systems. A 20 wt% TBAB solution has a latent heat of fusion of approximately 220 kJ/kg, and its clathrate hydrate suspension is a slurry with sufficient fluidity. The objective of this study is to examine the dynamic characteristics of the formation of TBAB clathrate hydrate. The schlieren system was used for simultaneous measurement of crystal growth and concentration field in TBAB aqueous solution. Results showed that the concentration diffusion layer of the leading edge of TBAB clathrate hydrate crystal moved with the crystal growth. Based on the measured spread rate and thickness of the diffusion layer, the diffusion coefficient of the TBAB molecule in the vicinity of solid-fluid interface was estimated.

A cobalt blue pigment having a core/shell structure was synthesized by solid phase synthesis of coated particles having Co(OH)2 particles adhered onto Al2O3 particles. In this research, the effect of mixing conditions on the color tone of synthesized pigment was investigated. As a result, it was found that the mixing time greatly affected the amount of adhered Co source particles, and the pressing force during mixing affected inhomogeneity of adhered amount of Co source particle on Al source particle surface. However, it was found that the inhomogeneity of the amount of Co source particles is small as the influence on the color tone of the calcinated product by diffusing onto the alumina surface of Co ions during calcination at high temperature. In addition, when the mixing conditions were not appropriate and the coating amount of the Co source particles on the Al source particles was small, the lightness of the product was high and the chroma was low. One reason for this is considered to be a decrease in the shell thickness generated by the decrease in the amount of Co source particles deposited. It was also suggested that the formation of black tri-cobalt tetroxide, which is an unreacted Co source not adhering to the Al source particles, is also the reason of the decrease of chroma of the product. [ABSTRACT FROM AUTHOR]

To improve the high-temperature oxidation resistance of grade S45C carbon steel, we formed a Cr / Ni diffusion layer on the surface of carbon steel by atmospheric-controlled induction heating fine particle peening (AIH-FPP) treatment. Cr and Ni particles were mechanically milled in planetary ball mills and used as shot particles in the AIH-FPP treatment to create a Cr / Ni diffusion layer. High temperature oxidation tests were carried out at 900°C for 100 hours to evaluate the high-temperature oxidation resistance of the AIH-FPP treated specimen. The mechanically milled particles and specimen were analyzed using a scanning electron microscope, an energy dispersive X-ray spectrometer, and an X-ray diffractometer. Results show that the AIH-FPP treated specimen prepared using mechanically milled particles formed a Cr / Ni diffusion layer on the carbon steel. The carbon steel sample with the Cr / Ni diffusion layer exhibited improved high-temperature oxidation resistance compared to the untreated sample. This is due to the formation of Cr and Ni oxidized layers on the treated surface, which inhibited oxidation of the inner substrate. The results indicate that a Cr / Ni diffusion layer formed by AIH-FPP treatment using mechanically milled particles can improve the high-temperature oxidation resistance of grade S45C carbon steel.

In order to compute hydrogen concentration distribution under mechanical loading, a stress-hydrogen diffusion or distribution coupling computing method had been developed based on Oriani’s theory. In this theory, it is assumed that hydrogen concentration between lattice sites and trapping sites are locally balanced, and a number of trapping sites are described as a function of equivalent plastic strain. In this study, this method was implemented to commercial finite element (FE) analysis software, Abaqus, with its user subroutine UMAT and UMATHT. This method was applied to analyze concentration of hydrogen near a blunting crack tip in pure iron. It is shown that the results of hydrogen distribution were nearly identical compared to the Sofronis’s study. Then, apparent diffusion coefficient and a relationship between the number of trapping sites and equivalent plastic strain were determined by using an electrochemical technique for high strength steel. The apparent diffusion coefficient was stable under elastic deformation; on the other hand it was drastically decreased as plastic strain increased. The material parameters were applied the blunting crack problem and the results were compared to that of pure iron. It is shown that hydrogen concentration of lattice site of high strength steel was more than three times as high as that of pure iron.

In this study, we developed a simultaneous measurement system for measuring the concentration fluctuations of two species using pulsed laser diodes in the light absorption spectrometric method. Conventional methods utilize halogen lamps or continuous laser diodes as light sources for concentration measurements. These light sources require multi-monochrometers or dichroic mirrors, which makes these methods rather expensive. However, using pulsed laser diodes as the light sources eliminates the need for additional multi-monochrometers and dichroic mirrors. A diffusion field consisting of two dye species in an axisymmetric turbulent jet was measured using the developed concentration measurement system. To ascertain the validity of our concentration measurements, we compared the present measurement results with those of a single dye species and previous studies. It was observed that the concentrations of the two dye species were measured accurately by the present measuring system. Therefore, such low-cost concentration measurement systems can be developed and applied in various simultaneous measurements of concentration fluctuations of multiple species such as in turbulent reactive flows.

Reactive centrifugal casting method could fabricate a Ni-aluminide/steel multilayer pipe. In this method, Ni powder is placed on a spinning steel pipe, and Al liquid was poured into the steel pipe. Then the Ni powder and Al liquid exothermically reacted and produced a composite layer consisting of Ni-aluminides on the inner surface of the steel pipe. The heat generated by the exothermic reaction melted the inner surface of the steel pipe and bonded the composite layer to the steel. In this study, fabrication of nickel/steel multilayer pipe by reactive centrifugal casting method is focused. However, during the above process, the Ni powder could move along the flow of the Al liquid. Moreover, sometime retained Ni powder was observed within the fabricated pipe, due to the lack of input heat. To overcome these shortcomings, in this study, Ni liquid as well as Al liquid was used for the reactive centrifugal casting method. Microstructure and ratio of joint region are studied. We focus on the effects of the pre-heating temperature and holding time, because these processing parameters can be easily controlled. Nickel layer and steel pipe are joined by the reactive centrifugal casting method under preheating-temperature from 700°C to 900°C. As preheating temperature increases, the ratio of the joint region is increased. Moreover, the ratio of the joint region is increased by heating the steel pipe under pre-heating temperature after the casting. Hence, it is found that the pre-heating and the heating after casting for the pipe are effective to join the nickel layer and the steel pipe.

Recently, spontaneously formed microwrinkles on hard coating-capped elastomer surfaces have attracted the attention of both the scientific and applied research communities, because of their simple fabrication process and potential for diverse practical applications. The depth and averaged orientation of the microwrinkle grooves can be controlled by applying strain. Here, we study the diffusion of light passed through a surface with wrinkles in the range of hundreds of microns. Without strain, the sample shows no wrinkles and is a transparent plate. With strain, the surface shows wrinkles and diffuses the light beam depending on the magnitude of applied strain. Thus, the present system can be used as a switchable optical diffuser. [ABSTRACT FROM AUTHOR]

The effect of molecular structure on interdiffusion of polymer/polymer bilayer films was investigated. Short-time relaxation at polymer/polymer interfaces with different molecular weights was also evaluated by in situ neutron reftectivity and analyzed based on various diffusion models. Interdiffusion of cyclic polystyrene/cyclic deuterated polystyrene was investigated as a function of temperature and molecular weight. Cyclic polystyrene, with weight-average molecular weight of 113k, being larger than the critical entanglement molecular weight for linear polystyrene, diffuses twice as fast as the corresponding linear one at all the temperatures employed. This result clearly shows that both the linear and cyclic polystyrenes have the same temperature dependence of segmental frictional coefficient and that the topology strongly affects the molecular motion of the whole chain. Molecular weight dependence of mutual diffusion coefficient of cyclic polystyrene is different from that of the linear one. The shorttime interdiffusion at an interface of linear polystyrene/linear deuterated polystyrene with different molecular weights was examined by time-resolved neutron reflectivity measurements. The model scattering length density profiles obtained by solving a partial differential equation for the diffusion process were used to analyze the data. These analyses reveal that even if the molecular weights of both components are larger than the critical molecular weight for entanglement, the initial interfacial broadening of bilayer films with different molecular weight proceeds with asymmetric mobility being proportional to N-1. [ABSTRACT FROM AUTHOR]

Three types of polyphenyleneoxide (PPO), whose density values are in the order of slowly cooled > melt quenched > CO2-conditioned, were prepared. The sorption measurements of Xe and CH4 and several techniques of 129Xe and ¹H NMR measurements were performed on each type. From the observed data, diffusion behaviors of the gases in PPO samples were discussed in detail. Attempts were made to characterize the fine higher-ordered structure of PPO in glassy state. After analyses of the sorption isotherms and the 129Xe NMR chemical shifts, it was concluded that the order of quantity of the un-relaxed volume, namely, degree of non-equilibrium state is slowly cooled < melt quenched < CO2-conditioned. The NMR peak width of gas molecules in PPO samples decreased with increasing pressure. This finding was semi-quantitatively interpreted by an assumption of two kinds of the gas molecules in PPO with different diffusivity values. This explained why diffusivity of the gas in PPO becomes higher with pressure. Applying this interpretation on peak width, we also confirmed that diffusivity values of the gas in slowly cooled, melt quenched, and CO2-conditioned increase in that order. In order to experimentally detect the multiple diffusion components, spin-spin relaxation time, we measured T2 because the observing time on diffusion behavior can be short as several hundreds of µs. The intensity of NMR signal of the gas in PPO sample shows almost single-exponential decay, therefore, one value of T2 was determined. Studies of temperature, pressure, and the degree of non-equilibrium, indicate that the qualitatively similar dependencies were obtained from this apparent T2 and thus the mean diffusion coefficient could be determined by gas sorption measurements. It could be said that T2 of the gas in PPO sample is a good indication of its diffusivity. On the other hand, the peak widths in a set of spectra obtained from T2 measurements decreased with increasing relaxation decay period. This means T2 relaxation of the gas in PPO sample is actually obeyed by multi-component processes. In other words, diffusivity of the gas is multiple for short time which corresponds to several tens of rim, after one converts the time to the mean distance moved by diffusion. From this diffusion behavior, it was estimated that the fine higher-ordered structure of PPO in glassy state is inhomogeneous on the several tens of nm level. Moreover, the order of this inhomogeneity was slowly cooled < melt quenched < CO2-conditioned. [ABSTRACT FROM AUTHOR]

Liquid crystalline aromatic polyester with n-tetradecyl side chains, B-C14 was synthesized from the 1,4-di-(n-tetradecyl ester) of 1,2,4,5-benzenetetracarboxylic acid and 4,4′-biphenol, to clarify the ability of magnetic orientation and gas transport properties of this polyester. B-C14 behaved as a thermotropic liquid crystal and formed a layered structure composed of alternating rigid aromatic main chain layers and flexible n-alkyl side chain layers. In this study, B-C14 membrane was prepared by annealing at 125°C for 12 h under a magnetic field (9.4 T), whose direction was perpendicular to the membrane surface. From WAXD studies, and solid-state 13C NMR CP/static measurements, we concluded that the layered structure of B-C14 aligned with the c-axis being perpendicular to membrane surface. From gas permeation measurements, we concluded that this successfully magnetic-oriented B-C14 membrane leads to a higher gas diffusion coefficient. [ABSTRACT FROM AUTHOR]

The diffusion and mobility of water in elongated and non-elongated specimens of polyamide (PA) 6 have been investigated. Water absorption was monitored by weighing the specimens, after they were immersed in distilled water. The mobility of water was evaluated by differential scanning calorimetry (DSC), by analyzing the freezing behavior upon cooling the water containing specimens to — 70°C. We found that the diffusion coefficient and the equilibrium water content increased in the elongated specimen. In addition, the absorbed water in non-elongated specimen exists as non-freezing bound water, probably due to the strong interaction with the amide groups, while in the highly elongated specimen a freezable bound water was clearly observed. These results suggest that some microstructural heterogeneities or inner defects, exist in the elongated specimen there exist in which the water molecules are accumulated and show much weaker interaction with the surrounding polymers. [ABSTRACT FROM AUTHOR]

The important point to mold a heat swelling microcapsule is to disperse uniformly without destroying a micro-balloon in the molded article. Accordingly the optimization of the steam pressure of the foaming reagent, the diffusion to the shell polymer, the heat-resistance of the shell polymer and character of gas barrier for is required. According to the technique of the multivariate analysis, the statistical model was designed and constructed for the foaming start temperature (Ts) and the maximum foaming temperature (Tmax), using the raw material value of the microcapsule which has core/shell structure, grain diameter distribution and for the stirring conditions. The faction to influence the Ts and Tmax could be specified by use of the statistical model. The core/shell constitution lowering the diffusion coefficient was applied to statistic models. It was necessary to use the increase of core weight, the cross-linking agent with low functional group in the presence of sodium hydroxide, simultaneously, and a narrow size distribution of the polymer in order to form the polymer at high temperature. In addition to, rotation number under polymerization conditions was found to influence the forming character. [ABSTRACT FROM AUTHOR]

Chemical compositions and those distributions of styrene (St) -methyl acrylate (MA) and St-ethyl acrylate (EA) copolymers synthesized by emulsion copolymerization under different polymerization conditions were examined by ¹H NMR and HPLC, respectively, results were compared with those of bulk copolymers. MA or EA fraction at early stage decreased with the increase of emulsifier concentration ([SDS], sodium dodecyl sulfate) and converged to the value calculated using the distribution factor (fd) when SDS concentration is extrapolated to zero. In St-MA copolymer, furthermore, MA fraction decreased with the increase of polymerization rates (Rp) and converged to the value from fd when Rp is zero. These results indicate that the MA or EA monomer fraction in micelle decreased compared to the expected value from fd due to the interaction of hydrophilic monomer with emulsifier and/or the diffusion-controlled process. From HPLC studies, it was, found that no homopolymer or copolymer with different composition was produced. [ABSTRACT FROM AUTHOR]

The diffusion behavior of an acid dye in Nylon 6 has been investigated as a dynamic dye distribution of two thermodynamically distinct populations of Langmuir type adsorption species and Partition type species. The sum of the dual concentration profiles was calculated by means of a finite difference method according to the Fick's second law. An improved dual diffusion equation gave a profile in good agreement with the experimentally apparent obtained literature profile for Orange II and Nylon 6 system under an over-dyeing condition. Thus the validity of the improved theory was confirmed. [ABSTRACT FROM AUTHOR]

We report on PVDF-based polymeric solid electrolytes (PSE) for dye-sensitized solar cells (DSCs). The dependence of the short-circuit current density (Jsc) on the diffusion coefficient was discussed on the basis of the equivalent circuit analysis of photocurrent in DSC. When the back electron transfer from TiO2 to an oxidized dye was taken into account, the diffusion coefficient dependence of Jsc was well explained. We confirmed that the Jsc of a PSE-based DSC with a 20 μm cell gap amounts to about 97% of that of a liquid-based DSC. We then focused on the cross-linking reaction of PVDF-HFP with amines. This cross-linking reaction allows us to carry out the otherwise inhibited in-situ reaction of the precursor inside a cell. We also studied DSCs fabricated with the cross-linked PVDF-HFP-based PSE. The energy conversion efficiency of the DSC was 4.8% with AM-1.5 illumination. [ABSTRACT FROM AUTHOR]

Polyethylene oxide (PEO) electrolytes doped with lithium salts have been studied by the multi-nuclear NMR methods for the glymes of the small molecular weights and the cross-linked solid polymers. The segmental motions of the PEO chain and the lithium hopping motions were analyzed from the spin-lattice relaxation times T1 of the ¹H and 7Li NMR. The diffusion phenomena were measured by the pulsed-gradient spin-echo (PGSE) NMR method for the individual components by ¹H, 7Li and 19F NMR (anions). When the solvents are liquids, all the components diffuse almost freely in the large temperature range; When the molecular weights of the solvents (polymers) become larger, the diffusion of the components become anomalous or restricted. The rate of the segmental motion relates with the glass transition temperature. The anion diffusion contributes mostly to the ionic conductivity. [ABSTRACT FROM AUTHOR]

The skin is not only the site of drug application, but also the site of exposure to various chemical substances. Prediction of skin permeability, body absorption, and local skin concentration of chemicals are very important to assure efficacy and safety. Most in silico models for skin permeation of chemical are based on the prediction of its permeability coefficient (P, unit cm/s), and a certain level of prediction accuracy has been obtained. On the other hand, the amount absorbed in the body of a chemical is calculated from the sum of the amount of skin permeation and the amount under the stratum corneum (viable epidermis and dermis). The amount of skin permeation can be calculated from the P value as mentioned above, however, the amount under the stratum corneum, which is related to the local skin safety of the chemical, cannot be predicted. This article describes the principles of permeation of chemicals across the skin, the relationship between skin permeability and concentration in the skin, and the method for calculating the chemical concentration under the stratum corneum using skin permeation parameters.