Acceleration or Suppression of α-Phase Precipitation Using Isothermal ω Phase in Ti-20 at.pct Nb Alloy

Homogeneous precipitation of a fine α phase in the β matrix of Ti alloys is a promising method for obtaining a highly strengthened Ti-based alloy. Isothermal ω particles are known to be the nucleation sites for fine α-phase precipitation, but an understanding of the kinetics of α-phase formation on isothermal ω particles is still lacking. This study aimed to reveal the effect of isothermal ω particles on α-phase precipitation onset time. Two-step isothermal aging of a Ti-20 at.pct Nb alloy after solid solution treatment at 1273 K (1000 °C) was carried out. The first step of the aging at 633 K (360 °C) involved the formation of isothermal ω particles in the β matrix. This was followed by a second aging step at 673 K, 723 K, and 773 K (400 °C, 450 °C, and 500 °C) for α-phase precipitation. Suppression of α-phase nucleation on the isothermal ω particles occurred at 673 K (400 °C), whereas acceleration of α-phase nucleation on the isothermal ω particles was observed at 723 K and 773 K (450 °C and 500 °C). Thermodynamic stability of the isothermal ω particles and solute partitioning were controlling factors for the α-phase precipitation kinetics.     

Study on laser consolidation of metal powder with Yb:fiber laser—Evaluation of line consolidation structure

This study describes the consolidation characteristics of chromium molybdenum steel (SCM) based powder used for rapid tooling. The laser beam used was a Yb:fiber laser with a spot diameter of 45 μm and a maximum power of 40 W. In order to investigate the influence of irradiation conditions on the maximum temperature at the focal area, a two-color pyrometer developed by the authors was used. In addition, the cross section of the consolidated structure was analyzed with an electron probe microanalysis, and the cutting force was measured with a dynamometer. The result showed that the maximum temperature at the focal area was related to the consolidation characteristics of the metal powder. The main parameters which affected the consolidation characteristics were laser power and scan speed of the laser beam. The deposited powder and the plate surface were melted with generated heat and alloyed in the process of the solidification. The specific cutting force was greatly influenced by the consolidation conditions. The highest value of a specific cutting force was obtained when the melting of the powder and the solidification of the molten powder were performed repeatedly and the structure was consolidated linearly.     

Adsorptive and photocatalytic removal of phenol by layered niobates organically modified through intercalation and silylation

Layered hexaniobate K4Nb6O17 was modified with dodecylammonium ions and octadecyltrimethoxysilane molecules, which were held in the interlayer spaces by electrostatic interactions and covalent attachment to the layers, respectively. Interlayer spacing of the niobate was expanded by incorporation of the bulky organic species. Vapor adsorption isotherms of benzene and water indicated hydrophobic interlayer microenvironments of the organically modified niobates. Both of the modified niobates fairly adsorbed phenol dissolved in water. The photocatalytic activity of hexaniobate allowed the organically modified materials to photocatalytically decompose phenol upon UV irradiation. Decomposition time courses and quantitative analysis of phenol present in the system indicated that the phenol molecules adsorbed on the niobates were preferentially degraded. XRD and IR analyses of the modified niobates indicated that the silylated niobate was more durable than the ion-exchanged sample; the former kept the structure during the photocatalytic process while the latter was partly collapsed.     

Porphyromonas gingivalis Lipopolysaccharides Promote Proliferation and Migration of Human Vascular Smooth Muscle Cells through the MAPK/TLR4 Pathway

Atherosclerosis is a major cause of mortality worldwide. The initial change in atherosclerosis is intimal thickening due to muscle cell proliferation and migration. A correlation has been observed between periodontal disease and atherosclerosis. Here, we investigated the proliferation and migration of human aortic smooth muscle cells (HASMCs) using Porphyromonas gingivalis-derived LPS (Pg-LPS). To elucidate intracellular signaling, toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (MyD88) of HASMCs were knocked down, and the role of these molecules in Pg-LPS-stimulated proliferation and migration was examined. The role of mitogen-activated protein kinase (MAPK) in HASMC proliferation and migration was further elucidated by MAPK inhibition. Pg-LPS stimulation increased the proliferation and migration of HASMCs and activated the TLR4/MyD88 pathway. TLR4 knockdown inhibited Pg-LPS stimulated HASMCs proliferation and migration. Pg-LPS stimulation led to the phosphorylation of P38 MAPK, JNK, and ERK, and MyD88 knockdown inhibited the phosphorylation of P38 MAPK and JNK but not ERK. P38 MAPK and SAPK/JNK inhibition did not suppress the proliferation of HASMCs upon Pg-LPS stimulation, but ERK inhibition significantly inhibited proliferation. SAPK/JNK and ERK inhibition suppressed Pg-LPS-stimulated migration of HASMCs. In conclusion, our findings suggest that Pg-LPS may promote atherosclerosis via the activation of MAPK through TLR4.     

Decomposition of a cyanine dye in binary nanosheet colloids of photocatalytically active niobate and inert clay

Binary colloids of inorganic nanosheets prepared by exfoliation of two different layered crystals form phase-separated structures with demixing of the two nanosheets. The phase-separated colloids of photocatalytic niobate and photochemically inert clay nanosheets exhibit unusual photochemical reactions based on the phase-separated structure. The present paper reports photocatalytic decomposition of a cyanine dye in this binary colloid, where the dye is selectively adsorbed on the clay nanosheets to be spatially separated from the photocatalytic nanosheets. Upon UV irradiation, the dye is photocatalytically decomposed in the colloids containing the niobate nanosheets, but self-photolysis of the dye is observed in the colloid lacking the photocatalytic nanosheets. Faster decomposition in nitrogen than in air suggests contribution of the conduction-band electrons generated in the niobate nanosheets to the photocatalytic reaction. In the binary colloid, the degradation is retarded compared with the single-component niobate colloid. Larger clay content more stabilized the dye against the decomposition. In contrast, irradiation of the colloids with visible light causes self-photolysis of the dye even in the presence of the niobate nanosheets, indicating the absence of electron transfer from the photoexcited dye to the photocatalytic nanosheets.     

Small Amounts of Rh-Promoted Ni Catalysts for Methane Reforming with CO2

Small amounts of Rh-promoted Ni/-Al₂O₃ catalysts possessed higher activity than pure Ni/-Al₂O₃, Rh-Al₂O₃ catalysts and exhibited excellent coke resistance ability in methane reforming with CO₂. XRD, H₂-TPR, CO₂-TPD and coking reaction (via CH₄ temperature-programmed decomposition) indicated that Rh improved the dispersion of Ni, retarded the sintering of Ni and increased the activation of CO₂ and CH₄ on the surface of catalyst.     

Effect of framework aluminum in proton‐ or copper‐exchanged MFI ferrialuminosilicates on their activity for the reduction of nitric oxide with ammonia

Reduction of NO with ammonia in excess oxygen has been carried out on protonform and Cu²⁺exchanged MFI ferrialuminosilicate. Though HZSM5 showed very low activity, the framework Al in Hferrialuminosilicate greatly enhanced the activity. The framework Al in Cu²⁺exchanged ferrialuminosilicate also enhanced the activity to some extent.     

焙烧对HZSM—5分子筛酸性的影响

本文运用ＦＴＩＲ及ＴＰＤ等手段，以氨和吡啶作探针，研究了焙烧温度和升温速率对分子筛儿酸性的影响。研究表明，随着焙烧温度的升高，ＨＺＳＭ－５分子筛骨架上的铝不断地从骨加上脱除下来进入分子筛道而形成骨架外铝，与此同时，分子筛的酸性受到影响较低温度时，对酸性的影响不大；高温焙烧则使得ＨＺＳＭ－５分子筛的Ｂ酸位大幅减少，Ｌ酸位有所增加，升温速率对ＨＺＳＭ－５分子筛的酸性基本无影响。