Large-sized Rods Research Articles

Preparation of Bi2O3-YSZ and YSB-YSZ Composite Powders by a Microemulsion Method and Their Performance as Electrolytes in a Solid Oxide Fuel Cell.

Bi2O3 is a promising sintering additive for YSZ that not only decreases its sintering temperature but also increases its ionic conductivity. However, Bi2O3 preferably grows into large-sized rods. Moreover, the addition of Bi2O3 induces phase instability of YSZ and the precipitation of monoclinic ZrO2, which is unfavorable for the electrical property. In order to precisely control the morphology and size of Bi2O3, a microemulsion method was introduced. Spherical Bi2O3 nanoparticles were obtained from the formation of microemulsion bubbles at the water-oil interface due to the interaction between the two surfactants. Nanosized Bi2O3-YSZ composite powders with good mixing uniformity dramatically decreased the sintering temperature of YSZ to 1000 °C. Y2O3-stabilized Bi2O3 (YSB)-YSZ composite powders were also fabricated, which did not affect the phase of YSZ but decreased its sintering temperature. Meanwhile, the oxygen vacancy concentration further increased to 64.9% of the total oxygen with the addition of 5 mol% YSB. In addition, its ionic conductivity reached 0.027 S·cm-1 at 800 °C, one order of magnitude higher than that of YSZ. This work provides a new strategy to simultaneously decrease the sintering temperature, stabilize the phase and increase the conductivity of YSZ electrolytes.

Characterization of precipitation, evolution, and growth of MnS inclusions in medium/high manganese steel during solidification process

MnS as a main manganese-containing inclusion in medium/high manganese steel, which can be determined to the mechanical properties of steel. However, the precipitation and evolution mechanism of MnS in medium/high manganese steel is still unclear due to the special solidification properties and element segregation behavior. Hence, the effects of sulfur content, manganese content and cooling rate on the precipitation, evolution, and growth behavior of MnS inclusions in medium/high manganese are various experimentally characterized and thermodynamically elucidated in the present work. The results of 2D and 3D observation indicated that the morphology of MnS in medium manganese steel were transformed from globular and spindle-like (type I MnS) into large-sized rods (type II MnS) and dendritic (type D MnS), when sulfur content was increased from 78 ppm to 1578 ppm. Particularly, the spatial distribution and structure of MnS inclusions are elaborated in detail through X-ray micro-CT observations, which are discussed by defining the quantitative topography parameters and statistical analysis. Based on in situ CSLM observations, MnS precipitation path in high sulfur medium manganese steel was monitored as L → (L + δ + MnS) → (δ + MnS) → (δ + γ + MnS) → (γ + MnS) → (α + γ + MnS) → (α+MnS). Simultaneously, the Scheil-solidification calculations demonstrated that MnS is precipitated at the interdendritic region where the solid-liquid states are coexisted, which is caused by the segregation of sulfur and manganese. Moreover, increasing sulfur content generates the earlier precipitation, and leads to the significant increase in the number and size of MnS inclusions. Besides, the increase of manganese content promotes the transition of MnS from globular to polyhedral shape, which is attributed to the dissociative eutectic reaction of MnS formation preferentially takes place earlier in case of high manganese steel. It is also found that the decreasing of cooling rate and increasing the manganese content tends to increase the number and size of MnS inclusions, which is resulted from the long growth times of high manganese steel induced by large solid-liquid temperature differences. This work provides a systematic understanding of the precipitation and evolution of MnS inclusions in medium/high manganese steel.

The Friction Force Determination of Large-Sized Composite Rods in Pultrusion

Nowadays, the simple pull-force models of pultrusion process are not suitable for large sized rods because they are not considered a chemical shrinkage and thermal expansion acting in cured material inside the die. But the pulling force of the resin-impregnated fibers as they travels through the heated die is essential factor in the pultrusion process. In order to minimize the number of trial-and-error experiments a new mathematical approach to determine the frictional force is presented. The governing equations of the model are stated in general terms and various simplifications are implemented in order to obtain solutions without extensive numerical efforts. The influence of different pultrusion parameters on the frictional force value is investigated. The results obtained by the model can establish a foundation by which process control parameters are selected to achieve an appropriate pull-force and can be used for optimization pultrusion process.

Axial rod growth and age estimation of the sea pen, Halipteris willemoesi Kölliker

Halipteria willemoesi is a large octocoral commonly found in the Bering Sea. It is a member of a ubiquitous group of benthic cnidarians called sea pens (Octocorallia: Pennatulacea). Sea pens have a skeletal structure, the axial rod, that in cross section exhibits growth rings. Pairs of adjacent rings, or ring couplets, were assumed to be annuli and were used to estimate the age and growth of H. willemoesi. Twelve axial rods, extracted from H. willemoesi collected in the Bering Sea, were selected to represent small (25-29 cm total length), medium (97-130 cm TL) and large (152-167 cm TL) colonies. Each rod resembled a tapered dowel; the thickest part (0.90-6.75 mm in diameter) was at about 5-10% of total length from the base tip, the distal part was more gradually tapered than was the base. The number of ring couplets increased with rod size indicating their utility in estimating age and growth. Estimated age among rods was based on couplet counts at the thickest part of each rod: the average estimated age (±SE) was 7.1 ±0.7, 19.3 ±0.5, and 44.3 ±2.0 yr for small, medium and large-size rods, respectively. Based on these estimated ages, average growth rate in total length was 3.9 ± 0.2, 6.1 ± 0.3, and 3 6 ± 0.I cm yr -1 for small, medium, and large-size colonies. The average annual increase in maximum rod diameter among all colonies was 0.145 ± 0.003 SE mm yr -1 ; therefore, age prediction from maximum rod diameter was calculated (estimated age (yr) = 7.0 * (maximum rod diameter, mm) -0.2; R 2 = 0.99). At maximize diameter, the average couplet width was relatively constant among the three colony sizes (0.072 ± 0.05 mm). X-ray diffraction and electron microprobe analyses revealed that the inorganic portion of the rod is composed of a high-magnesium calcite. Radiometric validation of these age and growth rate estimates was attempted, but high amounts of exogenous 210 Pb precluded using the disequilibria of 210 Pb: 226 Ra. Instead, 210 Pb activities were measured in a series of cores extracted along the axial rod. These activities ranged from 0.691 ± 0.036 (SE) to 2.76 ± 0.13 dpm g -1 , but there was no pattern of decay along the length of the rod; therefore, the growth rates and corresponding ages could not be validated. Based on estimated age from ring couplet counts, growth in total rod length is slow at first, fastest at medium size, and slows toward maximum size, with an estimated longevity approaching 50 yr.

ボンド・フラックスによるサブマージアーク溶接の研究(5報)

In the Petro-chemical industry, various equipments operating at low tempesatures are increasing, and generally Aluminum killed steel down to -46°C and 3.5% Nikel steel down to -101°C are used as low temperature service structural materials. For these low temperature materials including their weld metals, the properties specified in the relevant clauses of ASTM A-300 are to be satisfied. Detailed reports on the properties for Aluminum killed steel and 3.5% Nikel steel materials and on those of weld metals made reports were with coated electrode arc welding was published in the past, and also reports were made for the case of MIG welding. However, there are only few papers of submerged are welding which considered as most efficient among all automatic welding methods ever applied to this type of welding work.Therefore we experimentally processed several bonded fluxes intended for the specific use in a submerged arc welding method applicable to low temperature steels, and investigated various properties, particularly impact values, of such weld metals obtained with these bonded fluxes.The results of experiment are summarized as follows ;(1) In the case of Aluminum killed steels, weld metal made with either of B+H-540 or B+H-350 combination satisfies the low temperature specification of ASTM as these have good mechanical properties and low temperature impact values.(2) In the case of submerged arc welding, the low temperature properties of weld metal are affected greatly by flux compositions. Therefore, the use of flux having characteristics of a low hydrogen type with large amount of CaCO3 content is recommended. Also, the low temperature impact values obtained on the weld metal are better for multipass weldieg with a small current than single pass welding with a large current.(3) In the case of single pass welding for Aluminum killed steels with a large current, the H-525 flux to which Fe-Al and Ni are added is preferable, and the weld metal obtained on such well generally gives a good low temperature impact values.(4) 3.5% Nickel wire and H-350 flux combination gives a good results for 3.5% Nikel weld metal. Possible low temperature impact value can be improved by a weld made with a low hydrogen type flux and small diameter rod combination in comparison to one made with large size rods, since the former tends to have a higher deposit metal temperature rise which boosts up the weld metal cleanliness than the latter.

ボンド・フラックスによるサブマージドアーク溶接の研究(4報)

In the Petro-chemical industry, various equipments operating at low tempesatures are increasing, and generally Aluminum killed steel down to -46°C and 3.5% Nikel steel down to -101°C are used as low temperature service structural materials. For these low temperature materials including their weld metals, the properties specified in the relevant clauses of ASTM A-300 are to be satisfied. Detailed reports on the properties for Aluminum killed steel and 3.5% Nikel steel materials and on those of weld metals made reports were with coated electrode arc welding was published in the past, and also reports were made for the case of MIG welding. However, there are only few papers of submerged are welding which considered as most efficient among all automatic welding methods ever applied to this type of welding work.Therefore we experimentally processed several bonded fluxes intended for the specific use in a submerged arc welding method applicable to low temperature steels, and investigated various properties, particularly impact values, of such weld metals obtained with these bonded fluxes.The results of experiment are summarized as follows ;(1) In the case of Aluminum killed steels, weld metal made with either of B+H-540 or B+H-350 combination satisfies the low temperature specification of ASTM as these have good mechanical properties and low temperature impact values.(2) In the case of submerged arc welding, the low temperature properties of weld metal are affected greatly by flux compositions. Therefore, the use of flux having characteristics of a low hydrogen type with large amount of CaCO3 content is recommended. Also, the low temperature impact values obtained on the weld metal are better for multipass weldieg with a small current than single pass welding with a large current.(3) In the case of single pass welding for Aluminum killed steels with a large current, the H-525 flux to which Fe-Al and Ni are added is preferable, and the weld metal obtained on such well generally gives a good low temperature impact values.(4) 3.5% Nickel wire and H-350 flux combination gives a good results for 3.5% Nikel weld metal. Possible low temperature impact value can be improved by a weld made with a low hydrogen type flux and small diameter rod combination in comparison to one made with large size rods, since the former tends to have a higher deposit metal temperature rise which boosts up the weld metal cleanliness than the latter.