Performance of NiB inhibitor for PbSCC of alloy 600 in Pb-contaminated water and caustic solutions

Nickel-based iron-chromium alloys are used as steam generator (SG) tubing materials in nuclear power plants (NPPs) but experience intergranular stress corrosion cracking (IGSCC) and lead stress corrosion cracking (PbSCC) due to the harsh operating conditions of NPPs. In order to improve the integrity of SGs, many studies have sought suitable inhibitors for IGSCC, while those for PbSCC have been sought to a limited extent. In this study, the performance of nickel boride (NiB) as an inhibitor for PbSCC was evaluated. Nickel boride has been shown to be a good inhibitor for IGSCC of Alloy (or Inconel) 600 in a caustic aqueous solution containing no lead (Pb). No significant SCC was observed to occur in Alloy 600 tested in pure water under the slow strain rate test (SSRT) condition in this study. A mixed mode of IGSCC and TGSCC, however, occurred relatively easily in Alloy 600 tested in pure water containing lead oxide (PbO) at 315 °C. The susceptibility of Alloy 600 to SCC decreased with the addition of NiB, implying that NiB can be used as an inhibitor for PbSCC in Pb-contaminated water.     

Effect of added ionomer on morphology and properties of PP/organoclay nanocomposites

Ethylene-methacrylic acid ionomer (Surlyn) with concentration up to 20 wt% based on total weight of polymer resin was added into polypropylene (PP)/organoclay hybrids. The microstructure, rheological properties, crystallization properties and mechanical properties of the obtained nanocomposites have been investigated. The addition of ionomer markedly enlarged interlayer spacing of the platelets and led to an improved degree of exfoliation. Moreover, clay silicates were found to selectively disperse either inside the ionomer phase or at the phase boundary. Compared to the binary immiscible blends, an improved interfacial adhesion was achieved for PP/Surlyn/OMMT hybrids. Unlike PP/Surlyn binary blends, the viscoelastic properties of the hybrids significantly increased with increasing Surlyn concentration, which could be attributed to the improved clay dispersion and the contribution of silicate layers at the interface between PP and Surlyn. A synergistic role between Surlyn and clay was also found to suppress the crystallization of PP matrix. In addition, PP/Surlyn/OMMT hybrids exhibited superior tensile strain compared to the corresponding PP/PP-g-MA/OMMT. Both tensile strength and elongation at break showed maximum at Surlyn concentration of 5 wt%. By comparing the experimental tensile yield strength with model prediction, it was suggested that the clay platelets localized at the interface could play a role of interfacial activation to some extent.     

Piezoelectric and optical properties of ZnO thin films deposited using various O<Subscript>2</Subscript>/(Ar+O<Subscript>2</Subscript>) gas ratios

In this study, ZnO thin films were fabricated on a Pt(111)/TiO_x/SiO₂/Si substrate using the RF magnetron sputtering method. Then, the effect of the crystallization orientation and microstructure on the piezoelectric and optical properties of the ZnO thin film was investigated for various O₂/(Ar+O₂) gas ratios. When the O₂/(Ar+O₂) gas ratio was 50%, the intensity of the (002) peak corresponding to the preferred orientation of the ZnO thin film was a maximum and the minimum FWHM value of 0.56° was observed. The surface roughness of the ZnO thin film measured using AFM also had a minimum value of 16.43 °C at an O₂/(Ar+O₂) gas ratio of 50%. The piezoelectric characteristics of the ZnO thin film were measured using the pneumatic loading method (PLM) and the corresponding constant had the largest value of 11.9 pC/N at an O₂/(Ar+O₂) gas ratio of 50%. The transmittance of the ZnO thin film obtained from the transmittance curve using a spectrophotometer was slightly greater than 80% in the human visible light region at an O₂/(Ar+O₂) gas ratio of 50%. By using the refractive index data obtained from the transmittance curve and the Sellmeir dispersion relation, we can also predict the refractive index at a wavelength of 400 nm. When the O₂/(Ar+O₂) gas ratio was 50%, the refractive index was 2.043 and, at other gas ratios, the corresponding refractive indices were 2.004∼2.006. The band gap energies of the ZnO thin film were 3.27∼3.33 eV depending on the O₂/(Ar+O₂) gas ratio and were little affected by the variation of the oxygen inflow volume.     

Characteristics of Cheonggukjang produced by the rotative fermentation method

This study was to develop a processing method for improving the quality of a fermented soybean food, cheonggukjang. Bacillus sp. AS-2 isolated from traditionally fermented cheonggukjang was selected for the production of cheonggukjang with the rotative fermentation method (RFM). The pH value of cheonggukjang made by RFM (cRFM) was 6.1±0.25. The amount of crude protein (329.0±0.92 mg/g) and amino-type nitrogen (120.6±21.81 mg%) were similar to those in traditionally fermented cheonggukjang (cTFM). The amount of ammonium-type nitrogen was 173.0±1.72 mM/g and nearly 4 times lower than that in cTFM. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging values in the traditional product were between 1.62±0.08 and 1.27±0.05, while with the RFM, the values were between 1.38±0.02 and 0.78±0.20. The antioxidative activity of the sauce-type cRFM was approximately 1.7 times higher than that of cTFM. The sensory scores for cRFM were uniformly higher than those for cTFM.     

Physicochemical and antioxidative properties of selected barnyard millet (Echinochloa utilis) species in Korea

Food Science and Biotechnology - The purpose of this study was to analyze and report the nutritional and physicochemical properties of 13 barnyard millet varieties (Echinochloa spp.) in Korea....