Synthesis and Photocatalytic Activity of Single-Crystalline Hollow rh-In₂O₃ Nanocrystals

We report here for the first time the hollow, metastable, single-crystal, rhombohedral In₂O₃ (rh-In₂O₃) nanocrystals synthesized by annealing solvothermally prepared InOOH solid nanocrystals under ambient pressure at 400 °C, through a mechanism of the Kirkendall effect, in which pore formation is attributed to the difference in diffusion rates of anions (OH^– and O^2–) in a diffusion couple. The InOOH solid nanocrystals were prepared via a controlled hydrolysis solvothermal route by using In­(NO₃)₃·4.5H₂O as a starting material and glycerol–ethanol as a mixed solvent. The glycerol–ethanol mixed solvent plays a key role on the formation of the intermediate InOOH, thus the final product of rh-In₂O₃. The as-synthesized In₂O₃ nanocrystals present excellent photocatalytic degradation of rhodamine B (RhB) and methylene blue (MB) dyes, which present ∼92% degradation of RhB or MB after 4 or 3 h reaction in the presence of the as-synthesized In₂O₃ nanocrystals, respectively

High-temperature reaction kinetics of Inconel 617 in impure helium

Inconel 617 is the reference candidate material for the high-temperature gas-cooled reactor (HTGR) which is expected to contain traces of impurities in the primary circuit. The corrosion behaviors of Inconel 617 in a special impure helium atmosphere (PCO = 0μbar) were investigated at 750℃ and 980℃ in this work. The production of CO was observed above 830℃, which can be verified by the thermodynamic model of “microclimate reaction”. Compared with the corrosion phenomenon at 750℃, the oxide layer thinning, surface breakage, and mass loss were found at 980℃. Then, the reaction kinetics of this corrosion behavior at 980℃ was studied, and the influence factor controlling the reaction rate is the partial pressure of CO in the atmosphere. On this basis, a gas phase prediction model for the “microclimate reaction” is proposed, which can be utilized to predict the variation of CO content in the impure helium atmosphere during the corrosion process at 980℃. The model is in good agreement with the experimental gas data in this study and previous work. Further, the critical temperature of the microclimate reaction could be obtained by the kinetic model in this research, which is consistent with the previous results of thermodynamic calculation and corrosion experiments

Prediction of Flow and Temperature Distributions in a High Flux Research Reactor Using the Porous Media Approach

High thermal neutron fluxes are needed in some research reactors and for irradiation tests of materials. A High Flux Research Reactor (HFRR) with an inverse flux trap-converter target structure is being developed by the Reactor Engineering Analysis Lab (REAL) at Tsinghua University. This paper studies the safety of the HFRR core by full core flow and temperature calculations using the porous media approach. The thermal nonequilibrium model is used in the porous media energy equation to calculate coolant and fuel assembly temperatures separately. The calculation results show that the coolant temperature keeps increasing along the flow direction, while the fuel temperature increases first and decreases afterwards. As long as the inlet coolant mass flow rate is greater than 450 kg/s, the peak cladding temperatures in the fuel assemblies are lower than the local saturation temperatures and no boiling exists. The flow distribution in the core is homogeneous with a small flow rate variation less than 5% for different assemblies. A large recirculation zone is observed in the outlet region. Moreover, the porous media model is compared with the exact model and found to be much more efficient than a detailed simulation of all the core components

High-Temperature Corrosion Behavior of Incoloy 800H Alloy in the Impure Helium Environment

The helium coolant in the primary circuit of the high-temperature gas-cooled reactor (HTGR) contains traces of impurities, which can induce the corrosion of superalloys when exposed to elevated temperatures. The superalloy damage caused by the corrosion could threaten the safe operation of the reactor. In this work, the corrosion behavior of a representative superalloy (chromium-rich iron base alloy Incoloy 800H) was investigated under the impure helium at different typical temperatures of HTGR. An experimental setup developed for studying the high-temperature corrosion of superalloys was used to investigate the chemical reactions and corrosion behaviors of Incoloy 800H. It was found that CO2 is an important oxygen source in the reaction with chromium, and CO is released as the product. In addition, the observation and computation of the critical temperature (TC) of the reaction between CO2 and carbon in the alloy show that TC is much lower than that (TA) of the microclimate reaction, which indicates that CO2 can protect the scale from destruction. Furthermore, the slight decarbonization of the alloy was found above TC. Also, a model developed by the thermodynamic analysis was proposed to explain the mechanism of slight decarbonization and predict the critical temperature when the CO2-C reaction occurs. This work presents a guideline for protecting the oxide scale of superalloys used in HTGR

Synthesis of Adenine-Modified Reduced Graphene Oxide Nanosheets

We report here a facile strategy to synthesize the nanocomposite of adenine-modified reduced graphene oxide (AMG) via reaction between adenine and GOCl which is generated from SOCl₂ reacted with graphite oxide (GO). The as-synthesized AMG was characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), UV–vis absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and galvanostatic discharge analysis. The AMG owns about one adenine group per 53 carbon atoms on a graphene sheet, which improves electronic conductivity compared with reduced graphene oxide (RGO). The AMG displays enhanced supercapacitor performance compared with RGO accompanying good stability and good cycling behavior in the supercapacitor