Microstructure and mechanical properties of metastable lath martensite wires in the Fe-Ni-Cr-Al-C system produced by melt spinning in rotating water

Metastable lath martensite ( _L ) phase wires with high strengths have been produced in the Fe-Ni-Cr-Al-C alloy system by melt spinning in rotating water. These wires have a circular cross section and a white lustre and the wire diameter is in the range of 100 to 140m. The width and length of each lath in the _L phase are as small as about 0.3 and 2m, respectively. The _y, _f and _p are about 900 and 1650 MPa and 2.0% for the _L wires. The subsequent annealing causes an increase in _p as well as _y and _f and the attained values are about 1000 and 1700 MPa and 3.0% for Fe-10Ni-10Cr-6.5 Al-1.0C wire annealed at 773 K for 1 h owing to the precipitation strengthening of a very fine unidentified carbide and to a high density of dislocations and lath boundaries in the _L phase. Further annealing causes a significant decrease in _p through decomposition of _L to+M₇C₃+M₂₃C₆. Therefore, the high strength combined with relatively good ductility for the _L wires is interpreted as due to the suppression of the phase transformation of _L to a mixed structure of+M₇C₃+M₂₃C₆ by melt quenching.     

Microstructure and superconducting properties of rapidly-quenched copper-based alloys containing immiscible lead and bismuth elements

Copper-based superconducting alloys including finely dispersed f c c lead or h c p (Pb- Bi) particles in f c c copper matrix have been obtained by rapid quenching (Cu-M)_100-x Pb_x and (Cu-M)_100-x (Pb_0.6Bi_{0.4 x} (M = aluminium, silicon or tin;x < 10 at%) alloys containing immiscible elements such as lead and bismuth. The particle size and interparticle distance were about 30 to 130 nm and 20 to 200 nm for had particles and about 30 to 60 nm and 30 to 150 nm for (Pb- Bi) particles. The transition temperature,T _c, was in the range of 3.2 to 5.5 K for the Cu-M-Pb alloys and 6.2 to 6.3 K for the Cu-M-Pb-Bi alloys. Critical magnetic field,H _c2, and critical current density,J _c, for the later alloys were 0.47 to 0.93T at 4.2 K and 1.1 × 10⁵ to 2.7 × 10⁵ Am^–2 at zero applied field and 4.21 K. The mechanism of the appearance of such a soft-type superconductivity for the rapidly quenched copper-based alloys was discussed, and inferred to be due to the formation of a percolation path of a superconducting lead or Pb-Bi phase along the grain boundaries, sub-boundaries and/or tangled dislocations where the lead or Pb-Bi phase precipitated preferentially, rather than the proximity effect based on lead or Pb-Bi particles.     

High-field superconductivity in Al-O-Pb and Al-O-Pb-Bi sputtered films

The sputter-quenched Al _x O _y alloys containing lead and bismuth elements, which are insoluble to aluminium; have been found to exhibit a remarkably enhanced upper critical field,H _c2, which is higher by about 6 to 66 times than those of pure lead metal and Pb₆₀Bi₄₀ alloy. The sputtered structure consists of amorphous Al _x O _y and f c c lead or h c p (lead-bismuth) phases. The lead and phases disperse homogeneously in the amorphous matrix and their particle sizes and interparticle distances are about 10 to 20 nm and 5 to 20 nm, respectively, for lead and particles. The superconducting transition temperature,T _c, upper critical magnetic field,H _c2, at 4.3 K, and residual resistivity at 10 K are 7.74 K, 3.3 T and 2.09 × 105cm, respectively, for (Al-O)_92.8 Pb_7.2 and 7.45 K, 8.2 T and 1.70 × 106 cm, respectively, for (Al-O)_86.2(Pb_0.6 Bi_0.4)_13.8. The remarkable enhancement ofH _c2 is interpreted as being mainly due to a remarkable decrease of the coherence length resulting from a large reduction of the effective mean free path of electrons. Additionally, the fluxoid pinning force under applied field has also been markedly enhanced for the duplex structure films than for sputtered lead film, probably because of the change of the dispersed lead phase into a type-II superconductor and an effective fluxoid pinning action at the interface between Al _x O _y and fine lead particles.     

MiR-10a in Pancreatic Juice as a Biomarker for Invasive Intraductal Papillary Mucinous Neoplasm by miRNA Sequencing

New biomarkers are needed to further stratify the risk of malignancy in intraductal papillary mucinous neoplasm (IPMN). Although microRNAs (miRNAs) are expected to be stable biomarkers, they can vary owing to a lack of definite internal controls. To identify universal biomarkers for invasive IPMN, we performed miRNA sequencing using tumor-normal paired samples. A total of 19 resected tissues and 13 pancreatic juice samples from 32 IPMN patients were analyzed for miRNA expression by next-generation sequencing with a two-step normalization of miRNA sequence data. The miRNAs involved in IPMN associated with invasive carcinoma were identified from this tissue analysis and further verified with the pancreatic juice samples. From the tumor-normal paired tissue analysis of the expression levels of 2792 miRNAs, 20 upregulated and 17 downregulated miRNAs were identified. In IPMN associated with invasive carcinoma (INV), miR-10a-5p and miR-221-3p were upregulated and miR-148a-3p was downregulated when compared with noninvasive IPMN. When these findings were further validated with pancreatic juice samples, miR-10a-5p was found to be elevated in INV (p = 0.002). Therefore, three differentially expressed miRNAs were identified in tissues with INV, and the expression of miR-10a-5p was also elevated in pancreatic juice samples with INV. MiR-10a-5p is a promising additional biomarker for invasive IPMN.     

Corrosion rate of magnesium and its alloys in buffered chloride solutions

The effect of the buffer capacity of test solution on the corrosion rate of cast pure (>99.95 mass%) and high-purity (>99.9999 mass%) magnesium, and AZ31 and AZ91E has been studied. Their corrosion rates were measured gravimetrically in a pH 6.5 and a pH 9 borate buffer including chloride ions, and in a conventional chloride solution. Except for the AZ91E in the pH 6.5, the corrosion rates of all the examined materials depended solely on the pH of the test solution, although the materials had a variety of purity and alloying elements. Higher buffer capacity probably masked the detrimental effect of the “cathodic impurities”. The corrosion rates measured in the buffers were considered as giving the resistivity of the passive film to anodic reactions. The high-purity magnesium had a fair corrosion resistance even in conventional chloride solution.     

In Situ Observation of Phase Separation of a Barium Borate Melt in a Stable Immiscibility Region under Microgravity

The precipitation of droplets was directly observed on a BaO–B₂O₃ melt in a drop shaft experiment. This is the first time that precipitation of droplets has been observed in a 4.5 s drop test. The melt film of 4BaOz96B₂O₃ (mol%) held on a platinum wire loop was heated above the critical tem-perature to produce uniformity and was cooled down to the phase separation temperature range. Phase separation of the melt was observed directly with a video camera. The IR image of the melt was simultaneously detected with a CCD array and was converted into a two-dimensional thermograph.     

Synthesis of Thermally Stable χ-Alumina by Thermal Decomposition of Aluminum Isopropoxide in Toluene

Thermal decomposition of aluminum isopropoxide in toluene at 315°C resulted in χ-alumina that had high thermal stability, whereas the reaction at lower temperatures resulted in formation of an amorphous product. The χ-alumina thus obtained directly transformed to α-alumina at ∼1150°C, bypassing the other transition alumina phases, whereas the amorphous product transformed to γ-alumina and then to θ-alumina before final transformation to α-alumina. When the χ-alumina, solvothermally synthesized at 315°C, was recovered by the removal of the solvent at the reaction temperature, thermal stability of the product was improved further. This procedure is convenient because it avoids bothersome work-up processes that yield large-surface-area and large-pore-volume alumina.     

Formation of jennite from fumed silica

Hydrothermal reactions of fumed silica with lime at 80°C were studied at starting Ca/Si of 0.8–2.0 and water/solid ratio of 20 by weight under periods of reaction time from 10 to 100 days.In the early ages of reaction, CSH having weak and diffuse basal reflections between 10–15Å was formed. On prolonging the reaction, CSH from the starting Ca/Si of 1.2–1.5 crystallised to jennite, and that from the starting Ca/Si of 0.9 to 14Å tobermorite.Lattice parameters were determined on the well crystalline jennite obtained by the reaction for 100 days at the starting Ca/Si of 1.4; i.e. a_o 10.59, b_o 7.21, c_o 10.82Å, α 99.60°, β 97.78°, γ 109.85°. Its crystals were lath-like elongated parallel to b with (001) cleavage.It was confirmed that the synthetic jennite was converted to meta-jennite by losing a part of its water on heating in air at 90°C. At higher temperatures it became poorly crystalline, and then crystallised to β-CaSiO₃ and β-Ca₂SiO₄ at 800°C.