Blunt corners of WC grains induced by lowering carbon content in WC–12mass%Co cemented carbides

Habit planes at WC/Co interfaces were investigated from a viewpoint of carbon content in WC–12mass%Co cemented carbides by transmission electron microscopy (TEM). WC/Co interfaces typically consist of (0001) and { 10[`1]0} { 10bar{1}0} habit planes with blunt corners, which are very close to { 10[`1]1} { 10bar{1}1} habit plane. The sizes of the blunt corners increase as the carbon content decrease. The expansions of blunt corners are due to the change in interface energy caused by the variation of the carbon content. The change in interface energy is discussed in terms of the incoherency between the (0001) planes of the WC grains and the Co-phase.     

Mass transfer and holdup in gas-liquid cocurrent flow packed beds containing water-repellent particles

Water-repellent particles were prepared by spraying polytetrafluoroethylene (PTFE) on activated carbon. Gas-liquid volumetric mass transfer coefficient and holdup were determined in gas-liquid cocurrent upflow and downflow packed beds from the measurements of gas desorption and volume, respectively. As the PTFE loading increased, the gas-liquid volumetric mass transfer coefficients in both upflow and downflow modes were enhanced. Gas holdup in the upflow mode increased with the PTFE loading, while the dynamic liquid holdup in the downflow mode decreased. The enhancement of the mass transfer rate from gas to liquid can be explained by the effect of water-repellency on the surface of activated carbon.     

Preparations and tribological properties of soft-metal/DLC composite coatings by RF magnetron sputter using composite targets

This work reports the characteristics and tribological properties of both Ag/DLC nanocomposite coatings (RF-Ag-DLC) and Cu/DLC nanocomposite coatings (RF-Cu-DLC) with hydrogen-free DLC matrix deposited by RF magnetron sputtering using a concentric composite target (CCT). The CCT consisted of a C base target and metal tablet, and the tablet was located on the center of the base target concentrically where the etching rate by Ar ions is extremely low. By changing the diameter of Ag or Cu tablets in CCT, RF-Ag-DLC with an Ag concentration ranging from 6 to 65 at.% and RF-Cu-DLC with Cu concentration ranging from 7 to 75 at.% can be prepared. These coatings show a granular structure having Ag or Cu nano-crystals with a diameter ranging from 5 to 10 nm dispersed homogeneously in the hydrogen-free DLC matrix. The friction coefficient of DLC varied depending on the species and content of metal. The transition of the friction coefficient became stable when metal-rich tribofilms formed on the counterfaces.     

Seismic proof test of a reinforced concrete containment vessel (RCCV): Part 2: Results of shaking table tests

A 1/8-scale model was constructed of a reinforced concrete containment vessel (RCCV) used in the latest advanced boiling water reactors (ABWR). Shaking table tests were conducted on it with input motions corresponding to or exceeding a design earthquake assumed for a real Nuclear Power Plant.The objectives of the tests were to verify the structural integrity and the leak-proof functional soundness of the RCCV subjected to design earthquakes, and to determine the ultimate strength and seismic margin by an excitation that led to the model's collapse. The model, the test sequence and the pressure and leak test results were addressed in Part 1. The shaking table test method, the input motions and the test results, including the transition of the model's stiffness, natural frequencies and damping factors and the effects of vertical input motions and internal pressure on the model's characteristics and behavior, the load–deformation, the ultimate strength, the failure mode of the reinforced concrete portion and the liner plate are described here. The seismic safety margin that was evaluated by the energy input during the failure test to a design basis earthquake will be described in Part 3. The analytical results of simulation using the multi-lumped mass model will be described in Part 4.     

Radiation-induced polymerization of ethylene in a pilot plant. I. Bulk process

Radiation-induced bulk polymerization of ethylene was carried out with use of a pilot plant with a 10 liter reactor at pressures of 225–400 kg/cm², temperatures of 30–95°C, ethylene feed rates of 5–28 kg/hr, and dose rate of 3.8 × 10⁵ rad/hr. Characteristics of the process are mild polymerization conditions and capability of producing medium density polyethylene in powder form. The spacetime yield and molecular weight of polymer were in the range of 3.5 to 13.1 g/liter hr and 2.2 × 10⁴ to 14 × 10⁴, respectively. The space-time yield increased with mean residence time and 2.4 powders of pressure, and decreased with temperature. Molecular weight changed similarly with the reaction conditions. These results were consistent with those of the bench plant experiment and the scale effect was small. Polymer deposit to the reactor wall limited a period of continuous operation of the plant. The amount of deposited polymer was increased with the square of reaction time. The rate of polymer deposit was proportional to polymer concentration and to the cube of pressure. The polymer deposit cannot be solved in the bulk process.     

Preparation and properties of graft and block copolymers of poly(p-phenylene terephthalamide) with polybutadiene

Graft copolymers of polybutadiene (PBD) onto poly(p-phenylene terephthalamide) (PPTA) were prepared by the nucleophilic substitution of N-metalated PPTA with telechelic PBD having bromide end groups. Block copolymers were synthesized by the condensation reaction of telechelic PBD having acid chloride end groups with amino-group-terminated PPTA. The structure of these copolymers was identified by IR spectra. Graft and block copolymers contained PBD segments up to 85 wt % and 45 wt %, respectively. Thermomechanical analyses (TMA) proved the existence of distinctive primary absorption peak corresponding with T_g of PBD for both graft and block copolymers. The T_g's of both types of the copolymers were further ascertained by the DSC curves. TMA curves suggested that the microphase separation occurred between PPTA and PBD. The incorporation of PPTA segments into PBD increased the decomposition temperature compared with the blend polymer composed of PPTA and PBD with the same composition.     

Positive-temperature-coefficient effect of electrical resistivity below melting point of poly(vinylidene fluoride) (PVDF) in Ni particle-dispersed PVDF composites

This paper discusses the positive-temperature-coefficient effects of resistivity in Ni particle-dispersed poly(vinylidene fluoride) (PVDF) composites based on experiment results from SEM, DSC, and pressure-volume-temperature (PVT) measurements. The melting points of composites with Ni content of 20, 30, 40, and 50vol.% were equal to that of pure PVDF. The PTC effects in composites with Ni content of 40 and 50vol.% occurred at temperatures near the melting point of the PVDF matrix, whereas those in composites with Ni content of 20 and 30vol.% occurred at temperatures below the melting point of the PVDF matrix. We found that the PTC effect occurs even without melting of the matrix polymer. Moreover, we determined that a slight increase in specific volume at temperatures below the melting point of the matrix polymer acts fully as a driving force for forming a gap between fillers. This suggestion was backed up by theoretical analyses using percolation theory and a thermal-fluctuation-induced tunneling model.