New type of phenolic resin: Curing reaction of phenol‐novolac based benzoxazine with bisoxazoline or epoxy resin using latent curing agent and the properties of the cured resin

In this study, we aimed to reduce the cure time, and to lower the cure temperature of the benzoxazine compound. Therefore, curing reaction of benzoxazine with bisoxazoline or epoxy resin using the latent curing agent and the properties of the cured resins were investigated. The cure behavior of benzoxazine with bisoxazoline or epoxy resin using the latent curing agent was monitored by differential scanning calorimetry and measurements for storage modulus (G′). The properties of the cured resin were estimated by mechanical properties, electrical insulation, water resistance, heat resistance, and flame resistance. As a result, it was confirmed that by using the latent curing agent, cure time of benzoxazine and bisoxazoline or epoxy resin was reduced, and cure temperature was lowered. And it was found that the curing reaction using phenol‐novolac based benzoxazine (Na) as the benzoxazine compound could proceed more rapidly than that using bisphenol‐A based benzoxazine (Ba) as the benzoxazine compound. However, the cured resins from Ba and bisoxazoline or epoxy resin using the latent curing agent showed good heat resistance, flame resistance, and mechanical properties compared with those from Na and bisoxazoline or epoxy resin using the latent curing agent. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

PVDF/PMMA composite nanofiber fabricated by electrospray deposition: Crystallization of PVDF induced by solvent extraction of PMMA component

The crystallization of poly(vinylidene fluoride) (PVDF) was observed after the poly(methyl methacrylate) (PMMA) component was extracted from the PVDF/PMMA (50/50) composite nanofiber fabricated by electrospray deposition, even though the original composite showed a completely amorphous pattern in the wide‐angle X‐ray diffraction. The content of the β‐crystal form in the crystalline region depended on the PVDF/PMMA composite ratios and the type of solvents used for the extraction of the PMMA component, e.g., chloroform and toluene. Thus, the content of the β‐crystal form can be controlled by selecting the original PVDF/PMMA composition and the solvent used to extract the PMMA component. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Characterization of carbon nanofibers synthesized by microwave plasma-enhanced CVD at low-temperature in a CO/Ar/O2 system

The low-temperature synthesis of carbon nanofibers by microwave plasma-enhanced chemical vapor deposition using a CO/Ar/O₂ system and their characterizations were performed. At the optimum oxygen concentration of O₂/CO = 7/1000, vertically aligned CNFs can be synthesized at temperatures as low as 180 °C with growth rates of 4–6 nm/s. The diameter of bulk CNFs is about 50–100 nm and the surface of CNFs is covered by branching fibers and their nuclei with a diameter of about 5–20 nm. Not only the peaks originating from carbon chains, but also oxygen containing groups, such as CO and COC, are observed in the FTIR spectra. The CNFs growth rate is almost independent from the substrate temperature and it is concluded that an elementary process not on the substrates, but in the gas phase, is the rate-determining step in the present CO/Ar/O₂ microwave-plasma-enhanced CVD system.     

USE OF METAL ADSORBING COMPOUNDS (MAC) TO MITIGATE ADVERSE EFFECTS OF HEAVY METALS IN BIOLOGICAL UNIT PROCESSES

The presence of heavy metals on an intermittent basis in the influent of biological unit processes can lead to process upset and poor removal of organics. Heavy metal breakthrough from a pretreatment process may be caused by a number of reasons. In this study, the feasibility of adding metal adsorbing compounds (MACs) into a sequencing batch reactor (SBR) to mitigate the adverse effects of heavy metals breakthrough was investigated. A powdered activated carbon was found to be an effective MAC for heavy metals concentrations varying from 2 to 20mg/L. Organic removal efficiencies in a SBR using MACs were similar to those of a control SBR with no metals in the influent.     

High Resistance of Cu–Ferrierite to Coke Formation During NH3-SCR in the Presence of n-Decane

Selective catalytic reduction of NO _x by NH₃ over Cu–FER and Cu–ZSM-5 in the presence of n-decane and SO₂ was investigated. NO _x conversion over Cu–ZSM-5 decreased in the presence of n-decane, owing to inhibition of the active sites by coke formation. In contrast, coke formation was negligible over Cu–FER, which maintained its NO _x conversion activity even in the presence of decane. Coke formation was negligible over H–ZSM-5 and H–FER supports, which suggests that Cu species were involved in coke formation. Temperature-programmed reduction by H₂ and electron spin resonance spectroscopy indicated that [Cu–O–Cu]²⁺ was probably the Cu species involved in coke formation over Cu–ZSM-5.     

Polymorph control of calcium carbonate by reactive crystallization using microbubble technique

In this study, we used the minute gas–liquid interfaces around CO₂/NH₃ microbubbles as new reaction fields where the crystal nucleation progresses and developed a crystallization technique to control the polymorphism of calcium carbonate (CaCO₃). In the regions around the gas–liquid interfaces of CO₂/NH₃ microbubbles, Ca²⁺ and CO₃²⁻ ion concentrations can be adjusted because of the characteristic of the electric charge on the bubble surface and the decrease in CO₂ concentration based on unit bubble caused by minimization of bubble size, and because of the pH difference between local pH at the gas–liquid interface and overall pH in the bulk liquid caused by mixing of NH₃ with CO₂; hence, the polymorph change of CaCO₃ is expected to occur. CaCO₃ was crystallized at 298 K by a semi-batch type reaction in which CO₂/NH₃/N₂ bubbles were continuously supplied to an aqueous Ca(NO₃)₂ solution using a self-supporting bubble generator. The solution pH during crystallization was maintained at a constant level of 6.9–12.0 by adding HNO₃ and NH₄OH solution. The average bubble size (d_bbl) was varied in the range of 40–1000 μm by controlling the N₂ flow rate, and the molar ratio of CO₂/NH₃ (αCO₂/NH₃${\alpha }_{\text{C}{\text{O}}_2\text{/N}{\text{H}}_3}$) was set at a specified value of 0.20–1.00 at a constant CO₂ flow rate. The following results were obtained by varying solution pH, d_bbl, and αCO₂/NH₃${\alpha }_{\text{C}{\text{O}}_2\text{/N}{\text{H}}_3}$: at a constant d_bbl of 40 μm and αCO₂/NH₃${\alpha }_{\text{C}{\text{O}}_2\text{/N}{\text{H}}_3}$ of 0.20, vaterite and calcite were major products at a solution pH lower than 9.0 and at a solution pH greater than 11.0, respectively, while aragonite was crystallized predominantly in the solution pH range of 9.7–10.5; at a constant solution pH of 9.7 the crystallization of aragonite was accelerated remarkably with a decrease in αCO₂/NH₃${\alpha }_{\text{C}{\text{O}}_2\text{/N}{\text{H}}_3}$ and d_bbl.     

Die quenching limit of AA2024 aluminum alloy billet on servo press

Die quenching of AA2024 aluminum alloy billets was carried out on a servo press with ram-motion control of WC-20 mass%Co dies directly after solution heat treatment (SHT). To clarify the dependence on billet size for die quenching, two billets with a height of h₀ = 8 mm or 16 mm and with the same diameter of 16 mm were prepared. The cylindrical billets were heated in an electric furnace at 823 K and transferred to the press. Then the billets were uniaxially compressed with a reduction in height (Δh/h₀) of 2% or 5%, and further held between the dies. The sandwiching duration by dies (t_d.q.) was varied from 0 to 8 s. Based a measured temperature change, hardness and TG–DTA analysis, it is found that die quenching is successfully carried out without precipitation hardening only in the case of the billet with a height of 8 mm and t_d.q. > 6 s. The reduction in height is limited less than 5% by intergranular fracture on side surface of billet during the die quenching process.     

The effect of the hydrothermal treatment with aqueous NaOH solution on the photocatalytic and photoelectrochemical properties of visible light-responsive TiO2 thin films

The effect of the hydrothermal treatment with aqueous NaOH solution on the photoelectrochemical and photocatalytic properties of visible light-responsive TiO₂ thin films prepared on Ti foil substrate (Vis-TiO₂/Ti) by a radio-frequency magnetron sputtering (RF-MS) deposition method has been investigated. The hydrothermally treated Vis-TiO₂/Ti electrodes exhibited a significant increase in their photocurrent under UV and visible light irradiation as compared to untreated Vis-TiO₂/Ti electrode. SEM investigations revealed that the surface morphology of Vis-TiO₂/Ti are drastically changed from the assembly of the TiO₂ crystallites to the stacking of nanowires with diameters of 30–50 nm with increasing hydrothermal treatment time (3–24 h), accompanying the increase in their surface area. The separate evolution of H₂ and O₂ from water under solar light irradiation was successfully achieved using the Vis-TiO₂/Ti/Pt which is hydrothermally treated for 5 h, while the H₂ evolution ratio was 15 μmol h⁻¹ in the early initial stage, corresponding to a solar energy conversion efficiency of 0.23%.     

Identification of Ustilago cynodontis as a new producer of glycolipid biosurfactants, mannosylerythritol lipids, based on ribosomal DNA sequences

Mannosylerythritol lipids (MELs) are one of the most promising glycolipid biosurfactants known because of their multifunctionality and biocompatibility. The search for novel producers of MELs was undertaken based on the analysis of ribosomal DNA sequences on basidiomycetous yeasts. The bermuda grass smut fungus Ustilago cynodontis NBRC 7530, which taxonomically relates to Pseudozyma shanxiensis known as a MEL-C producer, was found to accumulate glycolipids in the cultured medium. Under a shake flask culture with soybean oil, the amount of the glycolipids was 1.4 g/L for 7 days at 25 degrees C. As a result of the structural characterization, the main glycolipids was identified as 4-O-[(4'-O-acetyl-3'-O-alka(e)noyl-2'-O-butanoyl)-beta-D-mannopyranosyl]-D-erythritol, and the major fatty acids were C(14) and C(16) ones. The glycolipid was highly hydrophilic MEL-C, and very similar to those produced by P. shanxiensis. The fungi of the genus Ustilago are thus likely to be potential producers of MELs as well as the yeasts of the genus Pseudozyma.