Deformation-induced martensitic transformation behavior in cold-rolled and cold-drawn type 316 stainless steels

We investigate deformation-induced martensitic transformation behavior in cold-rolled and cold-drawn specimens of type 316 stainless steel. Deformation-induced martensite preferentially nucleates at the twin boundary between the austenite matrix and a deformation twin. In the cold-rolled specimen, martensite formed at the twin boundary has a Kurdjumov–Sachs (K–S) relationship with both the austenite matrix and the deformation twin (“double K–S relationship”). In the cold-drawn specimen, two kinds of deformation twins with different twin planes are typically formed, and therefore deformation-induced martensites are formed where the deformation twin boundaries intersect: martensite thus has an imperfect “triple K–S relationship” with the austenite matrix and the two deformation twins. The complicated crystallographic orientation relationship between austenite and martensite grains strongly restricts the formation of some variants of deformation-induced martensites. Because of the difference in number of nucleation sites in the cold-drawn and cold-rolled specimens, martensitic transformation is more enhanced in the former than in the latter.     

Effect of Hydrogen Atmosphere on Pyrolysis of Cured Polycarbosilane Fibers

SiC-based fibers with various chemical compositions were synthesized using an irradiation-curing process. Polycarbosilane (PCS) fibers were cured by irradiation with an electron beam in a helium atmosphere. The cured PCS fibers were pyrolyzed at 1300°C under controlled hydrogen or argon atmospheres, and SiC fibers with C/Si of 0.84 to 1.56 were obtained. The fibers consisted of <1.0 wt% O, <0.2 wt% N, <0.1 wt% H, with the balance being Si and C. The mechanism of pyrolytic transformation of cured PCS to SiC-based ceramics was investigated using TG/DTA analysis. Greater mass losses were observed during pyrolysis in a hydrogen atmosphere than in argon. This result suggests that the hydrogen atmosphere suppresses H₂ evolution and helps to remove excess carbon as CH₄ during pyrolysis. The microstructure and mechanical properties of the resulting SiC-based fibers were found to be very dependent on their C/Si chemical compositions.     

In Situ Formation of Hexaferrite Magnets within a 3Y-TZP Matrix: La2O3–ZnO–Fe2O3 and BaO–Fe2O3 Systems

The in situ formation of magnetoplumbite-type (M-type) hexaferrites within a 3Y-TZP matrix was examined for the La₂O₃–ZnO–Fe₂O₃ and BaO–Fe₂O₃ systems. The formation of barium hexaferrite (Ba-M) was rapid enough at a temperature of 1300°C for 2 h to result in a uniform dispersion of fine Ba-M particles in a tetragonal zirconia polycrystal (TZP) matrix. However, the formation of lanthanum-substituted hexaferrite (La-M) was rather sluggish, despite the existence of a charge-compensating divalent oxide. The 3Y-TZP/20-wt%-BaFe₁₂O₁₉ in situ composite possessed good magnetic properties, as well as moderately good mechanical properties.     

Preparation and photocatalytic activity of Keggin-ion tungstate and TiO2 hybrid layer-by-layer film composites

Keggin ions (PW₁₂O₄₀³⁻ (PW₁₂), SiW₁₂O₄₀⁴⁻ (SiW₁₂), H₂W₁₂O₄₀⁶⁻ (H₂W₁₂)) and TiO₂ hybrid thin films were prepared using the layer-by-layer method. Their photocatalytic activities were investigated using gaseous 2-propanol decomposition. All films were transparent in the visible wavelength range. For 2-propanol decomposition, H₂W₁₂ was the most effective for the combination with TiO₂ despite having the smallest TiO₂ deposition amount. The photocatalytic activity of the PW₁₂–TiO₂ hybrid film was increased 2.3 times by visible light with UV illumination. This increase was less remarkable for hybrid films of other Keggin ions, suggesting that the visible light excitation of reduced PW₁₂ plays an important role in the enhancement of 2-propanol decomposition.     

Synthesis, Structure and Magnetic Properties of a Novel Anion-Radical Salt Based on TCNQ

Abstract  

A novel anion-radical salt, (Bbzim)(TCNQ)_1.5·CH₃CN (1), (where Bbzim = 1,3-bis(4-cyanobenzyl)-1H-imidazol-3-ium and TCNQ = 7,7,8,8-tetracyanoquinodimethane) has been fabricated and X-ray single crystal structural analyses. The structure analysis show there exist TCNQ⁻¹ and TCNQ⁰ entries, which are in agreement with the IR spectra analysis of the compound. Two TCNQ (A) and one TCNQ (B) molecules stack into a triad, and the triads further develop into a column in a pattern ···ABA···ABA··· along a-axis. The temperature dependence of the magnetic susceptibility (2–300 K) for 1 exhibits spin gap of singlet–triplet feature, and the best fit gave the Δ/k_B = 1236.5 K.     

Syntheses and Characterizations of Three Cu(II) Complexes with 2,2′-Bipyridine-3,3′-dicarboxylate and <Emphasis Type="Italic">N</Emphasis>-Donor Ancillary Ligands

Abstract  

Three novel inorganic–organic hybrid frameworks of [Cu(BPDC)(2,2′-bipy)] (1), [Cu(BPDC)(BIB)₂ ·H₂O]_n (2) and [Cu(BPDC)(4,4′-bipy)]_n (3) (BPDC²⁻ = 2,2′-bipyridine-3,3′-dicarboxylate; 2,2′-bipy = 2,2′-bipyridine; BIB = 1,2-bis(imidazol-1-ylmethyl)benzene; 4,4′-bipy = 4,4′-bipyridine) were prepared. The three complexes have been characterized by the elemental analyses, IR spectra, TGA and the single crystal X-ray diffraction. Two intramolecular Cu(II) centers of 1 are encircled by two BPDC²⁻ ligands forming an 18-membered ring, which is further assembled into a three-dimensional (3D) supramolecular architecture through the C–H···O hydrogen-bonding interactions. Complex 2 possesses a two-dimensional layer network, while complex 3 is a three-dimensional polymer composed of Cu-BPDC helical chains bridged by 4,4′-bipy. In addition, the electrochemistry of complex 1 was investigated.     

日本水坝的安全管理和地震安全评价

日本是一个地震多发的国家,而特殊的地形又决定了水坝在其经济社会发展中具有重要的地位,因此水坝的安全管理和地震安全评价就成为一个至关重要的方面.     

Scanning probe microscopy installed with nanotube probes and nanotube tweezers

We have developed well-controlled processes for the growth and manipulation of carbon nanotubes. The relatively thin multiwalled nanotubes were prepared with high purity by arc discharge with a high gas temperature. In the manipulation of nanotubes, the first crucial process is to prepare a nanotube array, so-called nanotube cartridge. We have found the alternated current electrophoresis of nanotubes by which nanotubes are aligned at the knife-edge of a disposal razor. The second important process is to transfer a nanotube from the nanotube cartridge onto a substrate in a scanning electron microscope. Using this method, we have developed nanotube probes and nanotube tweezers that operate in a scanning probe microscope (SPM). The nanotube probes have been applied for observation of biological samples and industrial samples to clarify their advantages. The nanotube tweezers have been demonstrated for their motion in scanning electron microscope and operated to carry a nanomaterial in a SPM.     

Anti-aging effects of caloric restriction: Involvement of neuroendocrine adaptation by peripheral signaling

Many hormonal signals from peripheral tissues contribute to the regulation of energy homeostasis and food intake. These regulators including leptin, insulin, and ghrelin, modulate the orexigenic and anorexigenic neuropeptide expression in hypothalamic nuclei. The anti-aging effects of caloric restriction have been explained from an evolutional viewpoint of the adaptive response of the neuroendocrine and metabolic response systems to maximize survival during periods of food shortage. In organisms, excess energy is stored in adipose tissues as a triglyceride preparation for such survival situations. Adipose tissue has recently been recognized as an endocrine organ, and leptin, as secreted by adipocyte, seems to be an especially important factor for the adaptive response to fasting and neuroendocrine alterations under caloric restriction. In this review, we discuss the potential involvement of neuroendocrine modulators in longevity and the anti-aging effects of caloric restriction.