Simulation of rubber isostatic pressing and shape optimization of rubber mold

An elastic–plastic FEM is developed to study the fundamental features of rubber isostatic pressing of powder with a view to performing a net-shape process. Experiments are also performed. It is thus shown that the properties of the rubber, in particular Poisson's ratio, give a great influence on the shape of compact and density distribution. The thickness of the rubber mold is also influential; the thicker the mold, the closer is the shape of compact to the cavity shape. An optimization scheme is also developed, so that one is able to determine the cavity shape that gives a desired shape of compact.     

Formation phenomena of iron oxide-silica composite in microwave plasma and DC thermal plasma

Iron oxide-silica composite was synthesized using atmospheric microwave plasma and DC thermal plasma. There has recently been increasing interest in predicting the final product during vapor phase synthesis using plasma because of difficulty obtaining desirable product. In this study, vapor phase synthesis of iron oxide-silica composite from iron pentacarbonyl (Fe(CO)₅) and tetraethyl orthosilicate (SiC₈H₂₀O₄, TEOS) was conducted using various Fe/Si ratios and different types of plasma to identify the formation mechanism in the Fe-Si-O multi-component system. The morphologies and phase compositions of the synthesized particles were analyzed and compared. The results showed that the Fe/Si ratio and the type of plasma influenced the morphologies and the phase composition. A thermodynamic consideration was introduced to investigate the particle formation phenomena, which could explain the differences induced by varying the Fe/Si ratio and type of plasma. The particle formation mechanism was divided into a condensation step and a diffusion step. At the condensation step, the Fe/Si ratio determined the condensation temperature, which is related to the morphology. At the diffusion step, the quenching rate of the plasma determined the degree of diffusion, which was related to the phase composition and formation of the external layer.     

Temperature dependence of birefringence and stress for natural rubber vulcanizates at strained state

The temperature dependence of stress and birefringence for natural rubber vulcanizates under medium and large deformation was measured for the processes of cooling, heating and re-cooling. In order to investigate the relation between the stress and crystal phase, the observed birefringence, Δt, was converted into the crystallinity, X_v, by the following equation:

$\text{X}{}_{\mathrm{<mtext>v</mtext>}}\text{=}\text{Δt?Δn}{}_{\mathrm{<mtext>a</mtext>}}\text{°f}{}_{\mathrm{<mtext>a</mtext>}}\text{Δn}{}_{\mathrm{<mtext>c</mtext>}}\text{°f}{}_{\mathrm{<mtext>c</mtext>}}\text{?Δn}{}_{\mathrm{<mtext>a</mtext>}}\text{°f}{}_{\mathrm{<mtext>a</mtext>}}$

where Δn⁰_c, Δn⁰_a, f_a and f_c are the intrinsic birefringence of the crystal, that of the amorphous phase, the orientation factor of crystallites, and that of amorphous phase, respectively. The fusion of crystallites induced by the thermal crystallization resulted in the increasing contractile force, while the fusion of strain-induced crystallites induced the reduction of contractile force.     

Fuel and emissions properties of Stirling engine operated with wood powder

From viewpoints of the environment and fuel cost reduction, small-scale biomass combined heat and power (CHP) plants are in demand, especially wood-waste fueled system, which are simple to operate and maintenance-free with high thermal efficiency similar to oil fired units. These are requested by wood and other industries located in mountainous region. To meet these requirements, a Stirling engine CHP system combined with simplified biomass combustion process with pulverized wood powder was developed.In an R&D project started in 2004 considering wood powder properties as a fuel, combustion performance and emissions in combustion flue gas were tested using combustion test apparatus with commercial size units. The wood powder combustion system was modified and optimized during the combustion test results, and the design of the demonstration plant combined with 55 kW_e Stirling engine power unit was considered. The demonstration plant was finally completed in March of 2006, and test operation has been progressed for the future commercial CHP system.In the wood powder combustion test, wood powder of less than 500 μm is mainly used, and a combustion chamber length of 3 m is applied. In these conditions, the air ratio can be reduced to 1.1 without increasing CO emission of less than 10 ppm and combustion efficiency of 99.9%. In the same conditions, NO_x emission is estimated to be less than 120 ppm (6% O₂ basis). Wood powder was confirmed to have excellent properties as a fuel for Stirling engine CHP system. This paper summarizes the wood powder combustion test, and presents the evaluation of the burner design parameters for the biomass Stirling engine system.     

Influence of physical relaxation on chemical stress–relaxation of natural rubber vulcanizates

Networks were prepared in the swollen and dry states to investigate the influence of physical relaxation on chemical stress–relaxation. The stress–relaxation behavior of solution-cured samples was different significantly from that of the samples crosslinked conventionally. The same result was also observed in the number of chain scission for both kinds of samples. On the other hand, the number of chain scission estimated by using the swelling method for samples crosslinked conventionally was in good agreement with that by the chemical stress–relaxation for solution-cured samples. It was found that there is little or no influence of the physical relaxation caused by entanglements, and no effect of dangling chains arising from scission in the equilibrium swelling. The relative change of network chain density determined by means of the swelling method was also consistent with that by sol fraction determination. These results indicate that the swelling method can be used as a measure of a degree of degradation on chemorheology. Taking into account the influence of physical relaxation on chemical stress–relaxation, a new relationship between the relative stress decay and the relative network chain density was experimentally proposed.     

D‐A1‐D‐A2 Backbone Strategy for Benzobisthiadiazole Based n‐Channel Organic Transistors: Clarifying the Selenium‐Substitution Effect on the Molecular Packing and Charge Transport Properties in Electron‐Deficient Polymers

Unipolar n‐type semiconducting polymers based on the benzobisthiadiazole (BBT) unit and its heteroatom‐substituted derivatives are for the first time synthesized by the D‐A₁‐D‐A₂ polymer‐backbone design strategy. Selenium (Se) substitution is a very effective molecular design, but it has been seldom studied in n‐type polymers. In this study, within the similar conjugated framework, the Se substitution effects on the optical, electrochemical, solid‐state polymer packing, electron mobility, and air‐stability of the target unipolar n‐type polymers are unraveled. Replacing the sulfur (S) atom in the thiadiazole heterocycles with the Se atom leads to narrower bandgaps and deeper lowest unoccupied molecular orbital (LUMO) levels of the n‐type polymers. Furthermore, the Se‐substituted polymer (pSeN‐NDI) shows shorter lamellar packing distances and stronger edge‐on π–π stacking interactions than its S‐counterpart (pSN‐NDI), as observed by the two‐dimensional grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) patterns. With the deeper LUMO level and thin‐film microstructures suitable for transistors, pSeN‐NDI exhibits four‐fold higher electron mobilities (μ_e) than pSN‐NDI. However, the other Se‐containing polymer, pSeS‐NDI, forms rather amorphous film structures, which is caused by its limited thermal stability and decomposition during the thermal annealing processes, thus giving rise to a lower μ_e than its S‐counterpart (pBBT‐NDI). Most importantly, pBBT‐NDI demonstrates an electron mobility of 0.039 cm² V^?1 s^?1, which is noticeable among the unipolar n‐type polymers based on the BBT and its analogs.     

Measurement of the 77Se(γ, n) cross section and uncertainty evaluation of the 79Se(n, γ) cross section

The ⁷⁷Se (γ, n) cross section was measured for the energy range from 7.6 to 13.8 MeV by using quasi-monochromatic laser-Compton scattering γ-rays. The advanced method to deduce γ-ray strength functions from (γ, n) cross section was developed. By utilizing the method, the γ-ray strength functions of ^{77, 78, 80}Se were deduced so as to reproduce the ^{77, 78, 80}Se (γ, n) cross sections measured in this work and previous systematic measurements. The inverse (n, γ) cross sections for ^{76, 77, 79}Se isotopes were calculated using the statistical model calculation code CCONE with the deduced γ-ray strength functions. The uncertainty of the calculated ⁷⁹Se(n, γ)⁸⁰Se cross section was evaluated by comparing the calculations and the experimental data on ^{76, 77}Se (n, γ) cross sections.     

Efficient characterization for protein crystals using confocal Raman spectroscopy

Confocal Raman spectroscopy was applied to the characterization of various states emerging in the screening of protein crystallization. Four main characterized states, namely single crystals, microcrystals, precipitates, and clear drops without solid materials, appear in a droplet for crystallization; the first three states should be critically distinguished and characterized because of the limitations of visual observation under an optical microscope. Using lysozyme and other proteins, crystallization was performed by the hanging drop vapor diffusion technique and was monitored through an automated confocal Raman system. Prior to the spectroscopic analysis, an optical microscope with a charge-coupled device (CCD) camera and associated image processing software were used to rapidly identify the XY locations to be measured spectroscopically by focusing the laser beam on a test sample. Instead of the current image analysis by optical microscopy, confocal Raman spectroscopy with a high spatial resolution was used to identify the state of protein crystallization. Such real-time Raman monitoring also distinguished real protein crystals from pseudo-protein crystals emerging in a crystallization droplet.     

Development of incremental deep drawing process

This paper deals with development of an incremental deep drawing process. On a newly developed incremental deep drawing set-up, the aluminium sheets are formed; the forming is carried out by deep-drawing the blank as in the conventional method but incrementally. Fractures at the punch or die corner in the blank may or may not occur depending on the conditions; the process parameters involved are punch size, punch corner radius, increment in punch displacement, blank holding force or pressure, etc. It is thus shown that different shapes are formed by one set of common tools. It is thereby confirmed that incremental deep drawing is possible without using a particular tool set for a particular shape.