Chemical interaction between granular B4C and 304L-type stainless steel materials used in BWRs in Japan

Chemical reactions between stainless steel and boron carbide were investigated using the materials applied for control rods in BWRs in Japan, specifically 304L-type stainless steel and granular boron carbide. The reaction region consisted of 2–4 layers, in which the significant composition variation of each element was detected, especially for B and C. Assuming that the reaction layer growth obeys the parabolic law, the effective rate constant between 304L-type stainless steel and granular boron carbide was evaluated to be approximately one order of magnitude smaller than the previously reported values for boron carbide pellets or powers. This difference might originate from the loose contact between the stainless steel and the granular boron carbide in the present study. Regarding liquefaction progress, the stainless steel components were selectively dissolved in the melt; consequently, the unreacted boron carbide tended to remain.     

Very Important Publication: Iridium‐Catalyzed Intramolecular Enantioselective C?H Alkylation at the C‐2 Position of N‐Alkenylindoles

Intramolecular enantioselective alkylation of N‐alkenylindoles proceeded via C H bond cleavage at the C‐2 position in the presence of a cationic iridium catalyst with a diphosphine ligand. Aroyl groups at the C‐3 position of the indoles operated as effective directing groups, and chiral 1‐substituted‐2,3‐dihydro‐1H‐pyrrolo[1,2‐a]indoles were obtained in high yield with excellent ee.

     

Preparation of an As(V) solution for scorodite synthesis and a proposal for an integrated As fixation process in a Zn refinery

A method for producing an As(V) solution from an As-bearing material obtained from a nonferrous hydrometallurgical process was investigated. Preparation of the As(V) solution included oxidative leaching of As with a NaOH solution, elimination of As as a calcium arsenate precipitate (johnbaumite: Ca₅(AsO₄)₃(OH)) with a Ca(OH)₂ secondary salt, washing the Ca–As compounds, and reaction of the Ca–As precipitate with H₂SO₄. This process was shown to be industrially applicable. The As ions and Cu ions were effectively separated by oxidative leaching with O₂ gas injection under strongly basic conditions. In this system, As dissolved in the NaOH solution and Cu precipitated with the residue. The dissolved As in this highly concentrated NaOH solution was then effectively precipitated from the solution by addition of a surplus amount of CaO, which allowed recycling of the NaOH solution. The addition of surplus Ca precipitated Ca₅(AsO₄)₃(OH) and Ca(OH)₂, which inhibited the leaching of As but did leach Ca and Na. When the Ca–As compounds were dissolved with H₂SO₄, Ca ions precipitated in the form of gypsum from the As-bearing solution. The gypsum produced by this process is likely to give rise to a number of As-related issues and the As level, therefore, needs to be reduced. This process is advantageous for the treatment of As since it is stabilized as scorodite. The production of an As(V) solution could be applied to hydrometallurgical operations as it necessary for the removal of As. This process is shown to be practically useful to As removal in Zn refining and a closed flow circuit is proposed for integration of this process into a Zn hydrometallurgical operation.     

High‐performance bio‐based thermosetting resins composed of dehydrated castor oil and bismaleimide

The reaction of dehydrated castor oil (DCO) and 1,1′‐(methylenedi‐4,1‐phenylene)bismaleimide (BMI) in 1,3‐dimethyl‐2‐imidazolidinone (DMI) at 130°C for 6 h and subsequent precipitation gave DCO/BMI prepolymer, which was cured at 200°C for 2 h gave DCO/BMI cured product. The FE‐SEM analysis revealed that the cured products with C?C ratio 2/1 and 1/1 are homogeneous, whereas phase separation occurs for the 1/2 product. The glass transition temperature, 5% weight loss temperature, and tensile modulus of the cured DCO/BMI increased with increasing BMI content. Regarding the tensile strength, the cured DCO/BMI 1/1 product showed the highest value. To evaluate the reaction of DCO and BMI, the model reaction products of DCO and N‐phenylmaleimide (PMI) in DMI were analyzed by ¹H NMR spectroscopy. The ¹H NMR data of DCO revealed that DCO has about 4.8 CH?CH bonds per triglyceride and that the ratio of conjugated and nonconjugated diene moieties is about 41/59. The NMR data of the reaction products of DCO/PMI with the C?C ratio 2/1 and 1/1 at 200°C for 24 h revealed that both Diels–Alder and ene reactions occurs in addition to radical polymerization. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and Properties of Woodceramic Thin Films

Woodceramic thin films were prepared onto alumina sheet and glass slide substrates by conventional radio frequency sputtering in an argon plasma. A woodceramic disk, 100 mm in diameter, sintered at 850°C was used as a target. The deposition rate was about 90 nm/h for 200 W input power. Remarkable differences were observed in the characteristics of films depending on the substrate temperature. Films prepared below 100°C had insulating properties, > 106 cm, and had transmission in the visible region ( > 600 nm), and had smooth surfaces. Increasing the substrate temperature causes sharp a decrease in the film resistivity and the growth of grain was 3–5 m. The film prepared at 300°C had semiconductor characteristics with an energy gap of about 0.05 eV.     

Flow stress analysis for determining the critical condition of dynamic ferrite transformation in 6Ni–0.1C steel

In order to clarify the occurrence of dynamic ferrite transformation in a 6Ni–0.1C steel, the stress–strain behavior in uniaxial compression was analyzed for a wide range of temperatures and strain rates. Significant softening of flow stress for austenite was observed at lower temperatures at a constant strain rate, which seemed to correspond with the occurrence of dynamic transformation to ferrite. Analysis of the maximum stress in the stress–strain curves indicated that dynamic ferrite transformation occurred above a certain value of the Zener–Hollomon parameter (Z). The critical deformation condition (Z_C) for the occurrence of dynamic transformation was determined. Increasing the amount of softening resulted in an increase in the fraction of ferrite, and the maximum flow stress came close to the flow stress of ferrite. Microstructural observations revealed that the specimens exhibiting softening consisted of ferrite grains with typical characteristics of deformation microstructure, such as a change in crystal orientation within the ferrite grain, inhomogeneity in ferrite morphology and dislocation substructures inside the grains. All these characteristics confirmed the occurrence of ferrite transformation during deformation, i.e. dynamic ferrite transformation.     

Development of torch position control and welding condition control technology for all‐position,multi‐layer GTA welding. Development of fully automatic GTA welding system for pipes (2nd Report)

In pulsed TIG welding, the current varies between two well-defined energy levels in a given frequency, thus being necessary to regulate a set of variables consisting of the peak current, peak time, background current, background time and the welding speed. Yet despite being a widespread technique, in practice, these welding variables are often regulated arbitrarily. This can lead to inefficient use of the pulsed current regarding the end result of the weld and aspects of productivity. This paper aims to present a roadmap developed in order to meet the practical need to establish criteria to assist in the determination of pulsed TIG welding variables, taking as its premise the desired width of the weld bead, overlap between the weld points comprising the weld bead and the welding speed. Finally, one application of this roadmap is presented in bead on plate welding of stainless steel plates with 1.2-mm thickness.