Microstructures and mechanical behavior of Inconel 718 fabricated by selective laser melting

In this study Inconel 718 cylinders were fabricated by selective laser melting in either argon or nitrogen gas from a pre-alloyed powder. As-fabricated cylinders oriented in the build direction (z-axis) and perpendicular to the build direction (x-axis) exhibited columnar grains and arrays of γ″ (body-centered tetragonal) Ni₃Nb oblate ellipsoidal precipitates oriented in a strong [2 0 0] texture determined by combined optical metallography, transmission electron microscopy, and X-ray diffraction analysis. Fabricated and hot isostatic pressed (HIP) components exhibited a more pronounced [2 0 0] columnar γ″ phase precipitate architecture parallel to the laser beam or build direction (spaced at ∼0.8 μm), and a partially recrystallized fcc grain structure. Fabricated and annealed (1160 °C for 4 h) components were ∼50% recrystallized and the recrystallized regions contained spheroidal γ′ precipitates distributed in a dense field of fine γ″ precipitates. The γ″ precipitates were always observed to be coincident with {1 0 0} planes of the γ-fcc NiCr matrix. Some δ phase precipitates in the unrecrystallized/recrystallized interfaces and recrystallized grain boundaries were also observed in the annealed samples. The microindentation (Vickers) hardness was 3.9 GPa for the as-fabricated materials, 5.7 GPa for the HIP material, and 4.6 GPa for the annealed material. Corresponding tensile properties were comparable with wrought Inconel 718 alloy.     

Dual-Function Semaphorin 4D Released by Platelets: Suppression of Osteoblastogenesis and Promotion of Osteoclastogenesis

Effects of the antiosteoblastogenesis factor Semaphorin 4D (Sema4D), expressed by thrombin-activated platelets (TPs), on osteoblastogenesis, as well as osteoclastogenesis, were investigated in vitro. Intact platelets released both Sema4D and IGF-1. However, in response to stimulation with thrombin, platelets upregulated the release of Sema4D, but not IGF-1. Anti-Sema4D-neutralizing monoclonal antibody (mAb) upregulated TP-mediated osteoblastogenesis in MC3T3-E1 osteoblast precursors. MC3T3-E1 cells exposed to TPs induced phosphorylation of Akt and ERK further upregulated by the addition of anti-sema4D-mAb, suggesting the suppressive effects of TP-expressing Sema4D on osteoblastogenesis. On the other hand, TPs promoted RANKL-mediated osteoclastogenesis in the primary culture of bone-marrow-derived mononuclear cells (BMMCs). Among the known three receptors of Sema4D, including Plexin B1, Plexin B2 and CD72, little Plexin B2 was detected, and no Plexin B1 was detected, but a high level of CD72 mRNA was detected in RANKL-stimulated BMMCs by qPCR. Both anti-Sema4D-mAb and anti-CD72-mAb suppressed RANKL-induced osteoclast formation and bone resorptive activity, suggesting that Sema4D released by TPs promotes osteoclastogenesis via ligation to a CD72 receptor. This study demonstrated that Sema4D released by TPs suppresses osteogenic activity and promotes osteoclastogenesis, suggesting the novel property of platelets in bone-remodeling processes.     

Determination of ethychlozate and its degradation product in fruits by HPLC and LC/MS

A method was developed for the analysis of ethychlozate (CIE) and its decomposition compound, 5-chloro-3(1H)-indazolylacetic acid (CIA) in fruits by HPLC and LC/MS. The sample was homogenized with 1 mol/L HC1, and CIE and CIA were extracted with 5 mol/L HCl and acetone. They were extracted from the acetone extract with diethylether-n-hexane (2:1). CIE was hydrolyzed to CIA with methanol-4 mol/L KOH (1:1). The solution was made acidic, and CIA was extracted with diethylether-n-hexane (2:1). The extract was cleaned up on a silica gel column. CIA was determined by HPLC-UV and LC/MS (Scan or SIR). Four fruits were spiked with CIE or CIA at 0.5 microgram/g and analyzed by the proposed method with HPLC. The average recoveries were 77.2-83.2% for CIE and 71.2-89.2% for CIA. The concentrations determined by LC/MS were 10-25% higher than the values by HPLC. The limit of detection (LOD) of CIA standard solution by HPLC corresponds to 0.015 microgram/g of CIE in the sample. In the same way, the LOD of CIA by LC/MS (SIR) corresponds to 0.009 microgram/g of CIE in the sample.     

Preparation of niobates of rhodium and nickel and their catalytic behaviors during calcination and reduction treatments

Double oxides of Rh and Ni have been prepared by chemical mixing methods. Silica-supported and unsupported RhNbO₄ and NiNb₂O₆ catalysts exhibited strong metal-oxide interaction behaviors in ethane hydrogenolysis activities after the decomposition of the double oxides by H₂ reduction at 500°C. Silica-supported and zeolite-supported RhVO₄ catalysts showed high activity and selectivity for dehydrogenation of cyclohexane after the decomposition in H₂. The double-oxide catalyst systems can be used as starting materials to obtain high-performance metal catalysts (redispersion of metals by H₂ reduction and regeneration of catalysts by calcination at a high temperature).     

Preparation and electrooptical properties of liquid crystal dispersed film by electron-beam irradiation

Polymer films consisting of nematic liquid crystal (LC) droplets and polymer networks were prepared by using a low-energy electron beam to irradiate a homogeneous mixture of nematic LC and bifunctional methacrylate monomer. Influences of such polymerization conditions as polymerization temperature, monomer concentration, and radiation energy on electrooptical properties of the compound films were examined. The polymer yield, affecting to a large extent the film properties, depended on the monomer concentration and the radiation energy. Compound films, which have a switching function from the scattering state to transparency by applying approximately 20–30 V between the two sides of the film, were obtained. In addition, it was found that a compound film with excellent electrooptical properties was prepared by changing impure LC in the droplets into pure LC. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1675–1681, 1997     

Observation of single-walled carbon nanotubes by photoemission microscopy

Single-walled carbon nanotube networks grown on SiO₂ pillars were studied by means of scanning photoemission microscopy. The individual nanotubes or nanotube bundles growing from the pillar tops were observed in C 1s images. Band bending near catalytic Fe/nanotube contacts in an end-bonded configuration was studied by measuring C 1s spectra along the tube axes. Within our experimental resolution, no band bending was observed. This implies that the depletion width is less than the spatial resolution of the scanning photoemission microscope (90 nm) or that the amount of the band bending is less than 0.1 eV.     

Characterization of doped single-wall carbon nanotubes by Raman spectroscopy

Single-wall carbon nanotubes were grown by thermal chemical vapor deposition using either boron- or nitrogen-containing feedstocks or both. Carrier doping was evidenced by hardenings of the G band in Raman spectra, and the estimated carrier concentration reached ∼0.4%. In the G′ and D band spectra, a doping-induced component was observed at the high- or low-energy side of the original one. However, the appearance of the new component did not always coincide with the carrier doping. The doped SWCNTs often show radial breathing mode peaks in the off-resonance region, indicating a defect-induced modification of absorption spectrum.     

Crystallization Behavior of Molecular Compound in Binary Mixture System of 1,3‐Dioleoyl‐2‐Palmitoyl‐sn‐Glycerol and 1,3‐Dipalmitoyl‐2‐Oleoyl‐sn‐Glycerol

Previous studies showed that the stable β‐form of molecular compound (MC) crystals having a double‐chain‐length structure is formed in a binary mixture system of 1,3‐dioleoyl‐2‐palmitoyl‐sn‐glycerol (OPO) and 1,3‐dipalmitoyl‐2‐oleoyl‐sn‐glycerol (POP) with a 1:1 concentration ratio of OPO and POP. The use of MC crystals made of POP and OPO for edible applications, such as margarine, is advantageous due to no‐trans, low‐saturated, and high‐oleic fats. Industrial manufacturing technology involves rapid cooling processes, and the kinetic properties of crystallization of MC of OPO and POP are required. In this study, we clarified the crystallization of MC of OPO and POP under rapid cooling at rates of 1–150 °C min^?1, using synchrotron radiation time‐resolved X‐ray diffraction and differential scanning calorimetry methods. The main results are as follows: (1) POP and OPO crystallized in separate manners without the formation of MC crystals under rapid cooling (>40 °C min^?1), while MC crystals started to form with decreasing rates of cooling in addition to the POP and OPO crystals (<30 °C min^?1); (2) metastable and stable forms sub‐α, α, β′, and β of POP and OPO were formed, whereas the MC crystals of β were formed during the cooling processes; and (3) the heating processes after crystallization by rapid cooling caused separate melting of the metastable and stable forms of POP and OPO crystals and the formation of MC crystals of β made of POP and OPO, as well as melting of the MC crystals alone.     

Simulation of thermophysical flow in axisymmetric nozzle with expansion chamber

Axisymmetric nozzle flows with a free‐jet expansion are simulated considering several substances and several flow conditions, and the thermophysical properties in the nozzle and the free‐jet region are predicted. The present numerical method is based on the preconditioning method developed by Yamamoto and the mathematical models of thermophysical properties of the substances. As numerical examples show, gas flows of carbon dioxide, water, and nitrogen under a subcritical pressure condition are first calculated. Calculated distances to the Mach disk are compared with the experimental results, and also the density distributions are compared among these three substances. Second, carbon dioxide flows while changing the pressure from subcritical to supercritical values are calculated and the effect of pressure on the flow field is investigated. Third, flows of water vapor with and without nonequilibrium condensation are calculated and the effect of condensation on the flow field is investigated. © 2010 American Institute of Chemical Engineers AIChE J, 2011